Dissertations / Theses on the topic 'Silicon nanocrystals'
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1
Walters, Robert Joseph Atwater Harry Albert. "Silicon nanocrystals for silicon photonics /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-06042007-160130.
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Choi, Jonghoon. "Silicon nanocrystals biocompatible fluorescent nanolabel /." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8806.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Sgrignuoli, Fabrizio. "Silicon nanocrystals downshifting for photovoltaic applications." Doctoral thesis, Università degli studi di Trento, 2013. https://hdl.handle.net/11572/368025.
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In conventional silicon solar cell, the collection probability of light generated carries shows a drop in the high energy range 280-400nm. One of the methods to reduce this loss, is to implement nanometre sized semiconductors on top of a solar cell where high energy photons are absorbed and low energy photons are re-emitted. This effect,
called luminescence down-shifter (LDS), modifies the incident solar spectrum producing an enhancement of the energy conversion efficiency of a cell. We investigate this innovative effect using silicon nanoparticles dispersed in a silicon dioxide matrix as active material. In particular, I proposed to model these structures using a transfer matrix approach to simulate its optical properties in combination with a
2D device simulator to estimate the electrical performance. Based on the optimized layer sequences, high efficiency cells were produced within the european project LIMA characterized by silicon quantum dots as active
layer. Experimental results demonstrate the validity of this approach by showing an enhancement of the short circuit current density with up to 4%. In addition, a new configuration was proposed to improve the solar cell performances. Here the silicon nanoparticles are placed on a cover glass and not directly on the silicon cells. The aim of this study was to separate the silicon nanocrystals (Si-NCs) layer from the cell.
In this way, the solar device is not affected by the Si-NCs layer during the fabrication process, i.e. the surface passivation quality of the cell remains unaffected after the application of the LDS layer. Using this approach, the downshifting contribution can be quantified separately from the passivation effect, as compared with the previous method based on the Si-NCs deposition directly on the solar devices. By suitable
choice of the dielectric structures, an improvement in short circuit current of up 1% due to the LDS effect is demonstrated and simulated.
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Sgrignuoli, Fabrizio. "Silicon nanocrystals downshifting for photovoltaic applications." Doctoral thesis, University of Trento, 2013. http://eprints-phd.biblio.unitn.it/944/1/Assemblaggio.pdf.
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In conventional silicon solar cell, the collection probability of light generated carries shows a drop in the high energy range 280-400nm. One of the methods to reduce this loss, is to implement nanometre sized semiconductors on top of a solar cell where high energy photons are absorbed and low energy photons are re-emitted. This effect,
called luminescence down-shifter (LDS), modifies the incident solar spectrum producing an enhancement of the energy conversion efficiency of a cell. We investigate this innovative effect using silicon nanoparticles dispersed in a silicon dioxide matrix as active material. In particular, I proposed to model these structures using a transfer matrix approach to simulate its optical properties in combination with a
2D device simulator to estimate the electrical performance. Based on the optimized layer sequences, high efficiency cells were produced within the european project LIMA characterized by silicon quantum dots as active
layer. Experimental results demonstrate the validity of this approach by showing an enhancement of the short circuit current density with up to 4%. In addition, a new configuration was proposed to improve the solar cell performances. Here the silicon nanoparticles are placed on a cover glass and not directly on the silicon cells. The aim of this study was to separate the silicon nanocrystals (Si-NCs) layer from the cell.
In this way, the solar device is not affected by the Si-NCs layer during the fabrication process, i.e. the surface passivation quality of the cell remains unaffected after the application of the LDS layer. Using this approach, the downshifting contribution can be quantified separately from the passivation effect, as compared with the previous method based on the Si-NCs deposition directly on the solar devices. By suitable
choice of the dielectric structures, an improvement in short circuit current of up 1% due to the LDS effect is demonstrated and simulated.
5
Deng, Xin, and 鄧欣. "Positron studies of silicon and germanium nanocrystals embedded in silicon dioxide." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41508749.
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Deng, Xin. "Positron studies of silicon and germanium nanocrystals embedded in silicon dioxide." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B41508749.
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Schmidt, Jan-Uwe. "Synthesis of silicon nanocrystal memories by sputter deposition." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28765.
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Aim of this work was, to investigate the preparation of Si NC memories by sputter deposition. The milestones are as follows: - Review of relevant literature. - Development of processes for an ultrathin tunnel-oxide and high quality sputtered SiO2 for use as control-oxide. - Evaluation of methods for the preparation of an oxygen-deficient silicon oxide inter-layer (the precursor of the Si NC layer). - Characterization of deposited films. - Establishment of techniques capable of probing the phase separation of SiOx and the formation of Si NC. - Establishment of annealing conditions compatible with the requirements of current CMOS technology based on experimental results and simulations of Si NC formation. - Preparation Si NC memory capacitors using the developed processes. - Characterization of these devices by suitable techniques. Demonstration of their memory functionality.
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Schmidt, Jan-Uwe. "Synthesis of silicon nanocrystal memories by sputter deposition." Forschungszentrum Rossendorf, 2005. https://hzdr.qucosa.de/id/qucosa%3A21703.
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Aim of this work was, to investigate the preparation of Si NC memories by sputter deposition. The milestones are as follows: - Review of relevant literature. - Development of processes for an ultrathin tunnel-oxide and high quality sputtered SiO2 for use as control-oxide. - Evaluation of methods for the preparation of an oxygen-deficient silicon oxide inter-layer (the precursor of the Si NC layer). - Characterization of deposited films. - Establishment of techniques capable of probing the phase separation of SiOx and the formation of Si NC. - Establishment of annealing conditions compatible with the requirements of current CMOS technology based on experimental results and simulations of Si NC formation. - Preparation Si NC memory capacitors using the developed processes. - Characterization of these devices by suitable techniques. Demonstration of their memory functionality.
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Ondič, Lukáš. "Silicon nanocrystals, photonic structures and optical gain." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE004/document.
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Les nanocristaux de Silicium (SiNCs) de taille inférieure à 5 nm sont des matériaux qui présentent une intense photoluminescence (PL) et capables d’amplification optique. Cette dernière propriété est un pré-requis à l’obtention d’émission stimulée sous pompage optique. Atteindre l’émission stimulé (et l’effet laser) à partir de nanostructures basées sur Si est d’un intérêt particulier dans le domaine de la photonique à base de silicium. Le but de ce travail était (i) d’étudier les propriétés optiques fondamentales de SiNCs, (ii) de concevoir et de réaliser un cristal photonique présentant une efficacité d’extraction augmentée et (iii) d’explorer la possibilité d’améliorer l’amplification optique des émetteurs de lumière à base de SiNCs en les combinant avec un cristal photonique à deux dimensionsSilicon nanocrystals (SiNCs) of sizes below approximately 5 nm are a material with an efficient room-temperature photoluminescence (PL) and optical gain. Optical gain is a prerequisite for obtaining stimulated emission from a pumped material, and the achievement of stimulated emission (and lasing) from Si-based nanostructures is of particular interest in the field of silicon photonics. The aim of this work was (i) to investigate fundamental optical properties of SiNCs, (ii) to design and prepare a photonic crystal with enhanced light extraction efficiency and (iii) to explore a possibility of enhancing optical gain of light-emitting SiNCs by combining them with a two-dimensional photonic crystal
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Brown, Samuel Lynn. "Silicon Nanocrystals| Optical Properties and Self-assembly." Thesis, North Dakota State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10790537.
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Silicon nanocrystal’s (SiNCs) size dependent optical properties and nontoxic nature portend potential applications across a broad range of industries. With any of these applications, a thorough understanding of SiNC photophysics is desirable to tune their optical properties while optimizing quantum yield. However, a detailed understanding of the photoluminescence (PL) from SiNCs is convoluted by the complexity of the decay mechanisms, including a stretched-exponential relaxation and the presence of both nanosecond and microsecond decays.
In this dissertation, a brief history of semiconductor nanocrystals is given, leading up to the first discovery of room temperature PL in SiNCs. This is then followed by an introduction to the various nanocrystal synthetic schemes and a discussion of quantum dot photophysics in general. Three different studies on the PL from SiNCs are then presented. In the first study, the stretched nature of the time dependent PL is analyzed via chromatically-resolved and full-spectrum PL decay measurements. The second study analyzes the size dependence of the bimodal PL decay, where the amplitude of the nanosecond and microsecond decay are related to nanocrystal size, while the third project analyzes the temperature and microstructure dependencies of the PL from SiNC solids.
After an indepth look at the PL from SiNCs, this report examines preliminary results of SiNC and silver nanocrystal self-assembly. When compared to metal and metal chalcogenide nanoparticles, there is a dearth of literature on the self-assembly of SiNCs. To understand these phenomena, we analyze the size dependent ability of SiNCs to form a ‘superlattice’ and compare this with silver nanocrystals. Although the results on self-assembly are still somewhat preliminary, it appears that factors such as SiNC concentration and size dispersity play a key role in SiNC self-assembly, while suggesting intrinsic differences between the self-assembly of SiNCs and silver nanocrystals.
Finally, at the end of this dissertation, a corollary project is presented on the computational analysis of fluorescent silver nanoclusters (AgNCs). Due to their small size and non-toxic nature, AgNCs are an ideal fluorophore for biological systems, yet there is a limited understanding of their photophysics, which is the focus of this part of the dissertation.
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Brown, Samuel. "Silicon Nanocrystals: Optical Properties and Self Assembly." Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/27926.
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Silicon nanocrystal?s (SiNCs) size dependent optical properties and nontoxic nature portend potential applications across a broad range of industries. With any of these applications, a thorough understanding of SiNC photophysics is desirable to tune their optical properties while optimizing quantum yield. However, a detailed understanding of the photoluminescence (PL) from SiNCs is convoluted by the complexity of the decay mechanisms, including a stretched-exponential relaxation and the presence of both nanosecond and microsecond decays. In this dissertation, a brief history of semiconductor nanocrystals is given, leading up to the first discovery of room temperature PL in SiNCs. This is then followed by an introduction to the various nanocrystal synthetic schemes and a discussion of quantum dot photophysics in general. Three different studies on the PL from SiNCs are then presented. In the first study, the stretched nature of the time dependent PL is analyzed via chromatically-resolved and full-spectrum PL decay measurements. The second study analyzes the size dependence of the bimodal PL decay, where the amplitude of the nanosecond and microsecond decay are related to nanocrystal size, while the third project analyzes the temperature and microstructure dependencies of the PL from SiNC solids. After an indepth look at the PL from SiNCs, this report examines preliminary results of SiNC and silver nanocrystal self-assembly. When compared to metal and metal chalcogenide nanoparticles, there is a dearth of literature on the self-assembly of SiNCs. To understand these phenomena, we analyze the size dependent ability of SiNCs to form a ?superlattice? and compare this with silver nanocrystals. Although the results on self-assembly are still somewhat preliminary, it appears that factors such as SiNC concentration and size dispersity play a key role in SiNC self-assembly, while suggesting intrinsic differences between the self-assembly of SiNCs and silver nanocrystals. Finally, at the end of this dissertation, a corollary project is presented on the computational analysis of fluorescent silver nanoclusters (AgNCs). Due to their small size and non-toxic nature, AgNCs are an ideal fluorophore for biological systems, yet there is a limited understanding of their photophysics, which is the focus of this part of the dissertation.NSF CBET-1133135
NSF CBET-1603445
DOE DE-FG36-08G088160
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Deokar, Geetanjali. "Cubic-silicon carbide nanocrystals epitaxied on silicon : synthesis and growth mechanism." Paris 6, 2012. http://www.theses.fr/2012PA066176.
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Nous présentons une technique originale de synthèse de nanocristaux de carbure de silicium cubique (3C-SiC) épitaxiés sur silicium et les résultats de l’étude des mécanismes de croissance des cristaux dans ces conditions. La technique consiste à recuire à 1100°C sous CO2 des substrats de silicium monocristallin recouverts de silice (épaisseur de quelques nm à 250 nm). La caractérisation par microscopie électronique atteste de la formation de nanocristaux de 3C-SiC à l'interface SiO2/Si, épitaxiés sur silicium sans apparition de défauts macroscopiques. De plus, l’utilisation de techniques telles que l’analyse par faisceau d’ions (réactions nucléaires, profil de concentration) ou la spectroscopie d’ions secondaires, nous a permis d’étudier en détail l'influence des paramètres expérimentaux (durée, pression de CO2, l'orientation du Si, épaisseur de silice) sur la croissance des cristaux de SiC. Nous avons ainsi montré que lors de sa diffusion dans la silice, le CO2 échange de l'oxygène avec le réseau de silice et nous avons pu déterminer la valeur du coefficient de diffusion de CO2 dans la silice à 1100°C Basé sur nos résultats, nous proposons un scénario pour la croissance de ces nanocristaux de SiC. La compréhension des mécanismes de croissance sera utile pour l'insertion de nanocristaux de 3C-SiC dans des dispositifs électroniques et optoélectroniques. Ces nanocristaux pourraient aussi servir de germes pour l’homoépitaxie de SiC ou l’hétéroépitaxie de GaN et, de films de diamantThis work aims to synthesis epitaxial 3C-SiC nanocrystals (NCs) on Si employing CO2 gas and to study the growth mechanism. The method consists in annealing SiO2/Si samples (with a silica thickness ranging from a few nm up to 250 nm) at 1100°C under a few hundreds of mbars of CO2. Epitaxial, void free 3C-SiC NCs formation at the SiO2/Si interface is evidenced by FE-SEM, TEM and AFM techniques. Moreover, the use of techniques such as ion beam analysis (nuclear reaction and narrow resonance profiles) or secondary ions spectroscopy allowed us to study in detail the influence on growth of SiC NCs of several experimental parameters such as the silica layer thickness, the substrate orientation, the annealing time duration and the CO2 pressure. We shown that, while CO2 diffuses through silica it exchanges oxygen with the silica network and we could determine the diffusion coefficient of CO2 in silica at 1100°C. Based on our study, we propose a model for SiC NCs growth. The understanding of SiC NCs nucleation site and growth mechanism could be useful for insertion of the as grown NCs in various applications for example, electronic and optoelectronic devices. These NCs can also be used as seeds for SiC homoepitaxial or heteroepitaxial GaN and diamond films
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Schnabel, Manuel. "Silicon nanocrystals embedded in silicon carbide for tandem solar cell applications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:da5bbb64-0bcd-4807-a9f3-4ff63a9ca98d.
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Tandem solar cells are potentially much more efficient than the silicon solar cells that currently dominate the market but require materials with different bandgaps. This thesis presents work on silicon nanocrystals (Si-NC) embedded in silicon carbide (SiC), which are expected to have a higher bandgap than bulk Si due to quantum confinement, with a view to using them in the top cell of a tandem cell. The strong photoluminescence (PL) of precursor films used to prepare Si-NC in SiC (Si-NC/SiC) was markedly reduced upon Si-NC formation due to simultaneous out-diffusion of hydrogen that passivated dangling bonds. This cannot be reversed by hydrogenation and leads to weak PL that is due to, and limited by, non-paramagnetic defects, with an estimated quantum yield of ≤5×10-7. Optical interference was identified as a substantial artefact and a method proposed to account for this. Majority carrier transport was found to be Ohmic at all temperatures for a wide range of samples. Hydrogenation decreases dangling bond density and increases conductivity up to 1000 times. The temperature-dependence of conductivity is best described by a combination of extended-state and variable-range hopping transport where the former takes place in the Si nanoclusters. Furthermore, n-type background doping by nitrogen and/or oxygen was identified. In the course of developing processing steps for Si-NC-based tandem cells, a capping layer was developed to prevent oxidation of Si-NC/SiC, and diffusion of boron and phosphorus in nanocrystalline SiC was found to occur via grain boundaries with an activation energy of 5.3±0.4 eV and 4.4±0.7 eV, respectively. Tandem cells with a Si-NC/SiC top cell and bulk Si bottom cell were prepared that exhibited open-circuit voltages Voc of 900 mV and short-circuit current densities of 0.85 mAcm-2. Performance was limited by photocurrent collection in the top cell; however, the Voc obtained demonstrates tandem cell functionality.
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Laube, Jan [Verfasser], and Margit [Akademischer Betreuer] Zacharias. "Silicon nanostructures: from isolated nanocrystals to percolated networks." Freiburg : Albert-Ludwigs-Universität Freiburg, 2017. http://d-nb.info/1128037092/34.
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Rafiq, Muhammad Aftab. "Electron transport in grown silicon nanocrystals and nanochains." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614342.
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Angeloni, Sara <1993>. "Silicon nanocrystals tailored for bioimaging and energy conversion." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9727/1/Angeloni_Sara_tesi.pdf.
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This thesis focus is the development of hybrid organic-inorganic systems based on Silicon Nanocrystals (SiNCs) with possible applications in the field of bioimaging and solar energy conversion. SiNCs were engineered thanks to the realization of a strong covalent Si-C bond on their surface, which allowed us to disperse them in different solvents with different final purpose. Chapter 1 introduces the basic properties of nanomaterials. Chapter 2 describes all the synthetic procedures to obtain the organic molecules-functionalized SiNCs. Chapter 3 illustrates an organic-inorganic antenna system based on SiNCs conjugated with diphenylanthracene (DPA) photoactive molecules, which was also embedded into Luminescent Solar Concentrators (LSC) made of a polymeric matrix. The optical and photovoltaic performances of this device were compared with the ones of a LSC embedded with a physical mixture made of SiNCs plus DPA at the same concentrations of the two components in the covalent system. Chapter 4 shows many different techniques to functionalize SiNCs with polyethylene glycol (PEG) chains in order to make them dispersible in water, for biomedical imaging applications. Chapter 5 presents the synthesis of dyes and/or SiNCs loaded Polymer Nanoparticles (PNPs) capable of excitation energy transfer (EET) mechanism. Chapter 6 is focused on the realization of photo-switchable systems based on azobenzene derivatives-functionalized SiNCs. These organic-inorganic hybrid materials were studied to possibly obtain a new light-driven response of SiNCs. In the end, chapter 7 reports the activity I followed in America, at The University of Texas at Austin, in the laboratory led by the professor Brian Korgel. Here I studied and compared the properties of high temperature hydrosilylated SiNCs and room temperature, radical promoted, hydrosilylated SiNCs.
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Prtljaga, Nikola. "Silicon nanocrystals: from bio-imager to erbium sensitizer." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/368704.
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The work in this thesis has been centred on the light emitting properties of silicon nanocrystals and the possible applications of this particular material platform to various topics ranging from bio-imaging to erbium ion sensitization. Silicon nanocrystals as bio-imaging agent have been investigated by employing colloidal dispersion of individual silicon nanocrystals where surface properties could be controlled to a great extent. By using a suitable functionalization scheme, high quality hydrophilic luminescent nanoparticles were produced. Using the improvements in the physical coating, bio-imaging on living cells (in vitro) was demonstrated showing that silicon nanocrystals have a great potential in bio-imaging and offer a promising alternative to commonly used fluorescence dyes.
A part from being good light emitters, silicon nanocrystals could also amplify the light. This is a reason why the part of the work in this thesis has been dedicated to the investigation of silicon nanocrystals as a gain material. While most of the studies on this topic are concentrated on the nanocrystal surface as a driving mechanism behind the optical amplification, the work presented in this thesis concerns the study of a zero phonon (direct) optical transition as a possible source of optical amplification in this material system. To this scope, investigation of the dynamics of the system on a nanosecond time-scale and under high excitation conditions has been employed. Additional insight on ultrafast dynamics has been obtained by using optical cavities in the form of optically active free-standing micro-disk resonators.
Finally, in the last part of this thesis a study of Er3+-doped Silicon-Rich-Oxide (SRO) materials and Er3+-doped SRO based devices is presented. This part of the work differs from the rest of the work reported in this thesis as is not focused on the light emitting properties of silicon nanocrystals but mostly on their non-radiative process engineering (energy transfer to erbium ions). Er3+ doped SRO opens the route towards compact waveguide amplifiers and lasers and allows for the possibility of electrical injection schemes, which are not realizable in standard erbium amplifiers used in EDFA for telecom applications. To that end, novel opto-electronic structures were proposed, modeled and manufactured and preliminary results of their performance were presented.
The sensitization mechanism between silicon nanoparticles and erbium ions was studied and its complex nature was illustrated. Although, the acquired knowledge of physics involved was not sufficient for formulation of a complete working theory of the energy transfer process, some important physical aspects of this process have been elucidated paving the way towards its complete understanding.
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Prtljaga, Nikola. "Silicon nanocrystals: from bio-imager to erbium sensitizer." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/715/1/Silicon_nanocrystals_from_bio-imager_to_Er3%2B_sensitizer.pdf.
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The work in this thesis has been centred on the light emitting properties of silicon nanocrystals and the possible applications of this particular material platform to various topics ranging from bio-imaging to erbium ion sensitization. Silicon nanocrystals as bio-imaging agent have been investigated by employing colloidal dispersion of individual silicon nanocrystals where surface properties could be controlled to a great extent. By using a suitable functionalization scheme, high quality hydrophilic luminescent nanoparticles were produced. Using the improvements in the physical coating, bio-imaging on living cells (in vitro) was demonstrated showing that silicon nanocrystals have a great potential in bio-imaging and offer a promising alternative to commonly used fluorescence dyes.
A part from being good light emitters, silicon nanocrystals could also amplify the light. This is a reason why the part of the work in this thesis has been dedicated to the investigation of silicon nanocrystals as a gain material. While most of the studies on this topic are concentrated on the nanocrystal surface as a driving mechanism behind the optical amplification, the work presented in this thesis concerns the study of a zero phonon (direct) optical transition as a possible source of optical amplification in this material system. To this scope, investigation of the dynamics of the system on a nanosecond time-scale and under high excitation conditions has been employed. Additional insight on ultrafast dynamics has been obtained by using optical cavities in the form of optically active free-standing micro-disk resonators.
Finally, in the last part of this thesis a study of Er3+-doped Silicon-Rich-Oxide (SRO) materials and Er3+-doped SRO based devices is presented. This part of the work differs from the rest of the work reported in this thesis as is not focused on the light emitting properties of silicon nanocrystals but mostly on their non-radiative process engineering (energy transfer to erbium ions). Er3+ doped SRO opens the route towards compact waveguide amplifiers and lasers and allows for the possibility of electrical injection schemes, which are not realizable in standard erbium amplifiers used in EDFA for telecom applications. To that end, novel opto-electronic structures were proposed, modeled and manufactured and preliminary results of their performance were presented.
The sensitization mechanism between silicon nanoparticles and erbium ions was studied and its complex nature was illustrated. Although, the acquired knowledge of physics involved was not sufficient for formulation of a complete working theory of the energy transfer process, some important physical aspects of this process have been elucidated paving the way towards its complete understanding.
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Alagoz, Arif Sinan. "Synthesizing Germanium And Silicon Nanocrystals Embedded In Silicon Dioxide By Magnetron Sputtering Technique." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608604/index.pdf.
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Applications of semiconductor nanocrystal in electronics are promising. Various techniques were developed to synthesize and analyze semiconductor nanocrystals for integrated circuit applications. In this study, silicon and germanium nanocrystals were synthesized in silicon dioxide matrix by magnetron sputtering deposition and following high temperature furnace annealing. Multilayer and single layer samples were prepared by co-sputtering depositions. Transmission electron microscopy measurements were carried out to analyze annealing effects on nanocrystal size distribution, change in shape, density and localization in silicon dioxide (SiO2). Ge-Ge Traverse Optical (TO) peak was monitored using Raman spectroscopy to investigate germanium nanocrystal formation and stress effects of silicon dioxide. Si-O-Si asymmetric stretching band is examined by Fourier transform infrared transmission spectroscopy to study silicon dioxide matrix recovery with germanium nanocrystal formation. Luminescence characteristics of silicon nanocrystals in visible and near infrared region (550nm-1050nm) with changing nanocrystal size and density were studied with photoluminescence spectroscopy.
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Scardera, Giuseppe ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics Faculty of Engineering UNSW. "Correlating structural and optical properties of silicon nanocrystals embedded in silicon nitride: An experimental study of quantum confinement for photovoltaic applications." Publisher:University of New South Wales. ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics, 2008. http://handle.unsw.edu.au/1959.4/41472.
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Silicon nanocrystals embedded in silicon nitride have received attention as promising materials for optoelectronic applications. More specifically, band gap engineering of novel materials based on silicon nanocrystals has been proposed for possible application in an all-silicon tandem solar cell within the field of `third generation' photovoltaics. Such an application would require nanocrystals to exhibit quantum confinement whereby the optical and electrical properties of a film could be tuned by controlling the size of these `quantum dots'. This thesis investigates the correlation between the structural and optical properties of silicon nanocrystals grown in silicon nitride multilayer structures via solid phase crystallisation, as part of an experimental investigation into quantum confinement. A study of the relevant processing parameters for the solid phase crystallization of silicon nanocrystals in amorphous silicon nitride is presented and the effectiveness of the multilayer approach for controlling nanocrystal size is demonstrated. Structural characterisation using transmission electron microscopy and glancing incidence x-ray diffraction is complemented with a new application of Fourier transform infrared spectroscopy for the detection of silicon nanocrystals. A case study on the effects of annealing temperature on the photoluminescence from silicon nitride multilayers is presented. While a clear correlation between the structural, molecular and optical properties is demonstrated, evidence of quantum confinement remains ambiguous. The investigation into the limits of parameter space for the formation of silicon nanocrystals in silicon nitride multilayers also leads to the formation of a novel Si-Si3N4 nanocomposite material. A comprehensive study of the photoluminescence from silicon nanocrystals embedded in nitride is presented in the context of homogeneous and multilayer nitride films. Size dependent PL and absorption is demonstrated for silicon nitride multilayers with silicon-rich silicon nitride layer thicknesses varying from 1 to 4.5 nm, indicating the formation of quantum wells. These same structures are annealed to form arrays of silicon nanocrystals. Although the PL and absorption spectra suggest quantum effects, inherent ambiguities remain. The findings in this thesis provide greater insight into the nature of confinement and indicate the need for further research if the successful implementation of these structures into an all silicon tandem cell is to be achieved.
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Flynn, Christopher Richard ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics Faculty of Engineering UNSW. "Sputtering for silicon photovoltaics: from nanocrystals to surface passivation." Awarded by:University of New South Wales. ARC Centre of Excellence in Advanced Silicon Photovoltaics & Photonics, 2009. http://handle.unsw.edu.au/1959.4/44686.
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Deposition of thin material films by sputtering is an increasingly common process in the field of silicon (Si)-based photovoltaics. One of the recently developed sputter-deposited materials applicable to Si photovoltaics comprises Si nanocrystals (NCs) embedded in a Si-based dielectric. The particular case of Si nanocrystals in a Silicon Dioxide (SiO2) matrix was studied by fabricating metal-insulator-semiconductor (MIS) devices, in which the insulating layer consists of a single layer of Si NCs in SiO2 deposited by sputtering (Si:NC-MIS devices). These test structures were subjected to impedance measurements. The presence of Si NCs was found to result in two distinct capacitance peaks. The first of these peaks is attributable to the small signal response of states at the insulator/substrate interface, enhanced by the presence of fixed charge associated with the NC layer. The second peak, which occurs without precedent, is due to external inversion layer coupling, in conjunction with a transition between tunnel-limited and semiconductor-limited electron current. Si:NC-MIS devices are also potential test structures for energy-selective contacts, based on SiO2/Si NC/SiO2 double barrier structures fabricated by sputtering. Using a one-dimensional model, current-voltage (I-V) curve simulations were performed for similar structures, in which the Si NCs are replaced by a Si quantum well (QW). The simulations showed that for non-degenerately doped Si substrates, the density of defects in the SiO2 layers can strongly influence the position of I-V curve structure induced by QW quasi-bound states. Passivation of crystalline Si (c-Si) surfaces by sputter-deposited dielectric films is another major application of sputtering for Si photovoltaics. This application was explored for the cases of sputtered SiO2 and hydrogenated Silicon Oxy-Carbide (SiOC:H). For the case of sputtered SiO2, an effective surface recombination velocity of 146 cm/s was achieved for an injection level of 1E15 cm???3. The investigated SiOC:H films were found to be unsuitable for surface passivation of Si, however their passivation performance could be slightly improved by first coating the Si surface with a chemically-grown or sputtered SiO2 layer. The investigations performed into specific aspects of sputter-deposited SiO2, Si NCs, and SiOC:H have highlighted important properties of these films, and confirmed the effectiveness of sputtering as a deposition technology for Si photovoltaics.
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Zelenina, Anastasiya [Verfasser], and Margit [Akademischer Betreuer] Zacharias. "Silicon nanocrystals in various dielectric matrices: structural and optical properties." Freiburg : Universität, 2016. http://d-nb.info/1119717361/34.
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Miller, Joseph Bradley. "Optical Properties and Ensemble Characteristics of Size Purified Silicon Nanocrystals." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27408.
Full textAbstract:
Nanotechnology is at the forefront of current scienti c research and nanocrystals
are being hailed as the `arti cial' atoms of the 21st century. Semiconducting silicon
nanocrystals (SiNCs) are prime candidates for potential commercial applications
because of silicon's already ubiquitous presence in the semiconductor industry,
nontoxicity and abundance in nature. For realization of these potential applications,
the properties and behavior of SiNCs need to be understood and enhanced.
In this report, some of the main SiNC synthesis schemes are discussed, including
those we are currently experimenting with to create our own SiNCs and the one
utilized to create the SiNCs used in this study. The underlying physics that governs
the unique behavior of SiNCs is then presented. The properties of the as-produced
SiNCs are determined to depend strongly on surface passivation and environment.
Size puri cation, an important aspect of nanomaterial utilization, was successfully
performed on our SiNCs though density gradient ultracentrifugation. We demonstrate
that the size-puri ed fractions exhibit an enhanced ability for colloidal self-assembly,
with better aligned nanocrystal energy levels which promotes greater photostability
in close-packed lms and produces a slight increase in photoluminescence (PL)
quantum yield. The qualities displayed by the fractions are exploited to form
SiNC clusters that exhibit photostable PL. An analysis of SiNC cluster (from
individual nanocrystals to collections of more than one thousand) blinking and
PL shows an improvement in their PL emitting `on' times. Pure SiNC lms
and SiNC-polymer nanocomposites are created and the dependence of their PL
on temperature is measured. For such nanocomposites, the coupling between the
`co ee-ring' e ect and liquid-liquid phase separation is also examined for ternary
mixtures of solvent, polymer and semiconducting nanocrystal. We discover that
with the right SiNC-polymer concentration and polymer molecular weight, phase separation can be supressed; we use this to build a prototype nanocomposite printing
device. Finally, the nanocrystals are PEGylated and introduced into an aqueous
biological environment to demonstrate their potential for use in biological labelling
and sensing devices. The development of superlattice structures from monodisperse
SiNC fractions and their use in solid-state lighting and solar cell applications are also
explored.
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Pringle, Todd Andrew. "Non-Thermal Plasma Synthesis of Luminescent Silicon Nanocrystals from Cylclohexasilane." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/31690.
Full textAbstract:
In this report we establish cyclohexasilane (CHS) as a reliable precursor for non-thermal plasma synthesis of high quality photoluminescent silicon nanocrystals (SiNCs). We demonstrate that this synthesis approach can produce high quality, size tunable silicon quantum dots with quantum yields exceeding 60% as synthesized (subsequent work in our group has measured over 70% quantum yield after density gradient ultracentrifugation size purification).After a brief background on non-thermal plasma synthesis, the characterization methods used in this study, and an overview of CHS, we report at length on our development of the apparatus used, and our exploration of the controllable processing parameters of the synthesis method. We describe our successes and challenges with size tuning, sample collection, and passivation. Finally, we discuss preliminary studies we performed to identify promising future research areas. Novel reactor designs, blue light passivation, and magnetic confinement of plasma are described briefly to entice future researchers.
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Wilkinson, Andrew Richard. "The optical properties of silicon nanocrystals and the role of hydrogen passivation /." View thesis entry in Australian Digital Program, 2006. http://thesis.anu.edu.au/public/adt-ANU20060202.111537/index.html.
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Ruhge, Forrest. "EFFECT OF GERMANIUM DOPING ON ERBIUM SENSITIZATION IN THE ERBIUM DOPED SILICON RICH SILICA MATERIAL SYSTEM." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2933.
Full textAbstract:
The continued size reduction in electronic integrated circuits has lead to a demand for on-chip high-bandwidth and low loss communication channels. Optical interconnects are considered an essential addition to the silicon electronics platform. A major challenge in the field of integrated Si photonics is the development of cost effective silicon compatible light sources. This thesis investigates the sensitization of group IV doped silica films emitting at 1.535μm for applications as silicon compatible light sources. Thin erbium-doped silica films containing excess silicon and germanium were deposited using a multi-gun sputter system. The composition of the deposited materials was verified by Rutherford Backscattering Spectrometry. Samples from each deposition were annealed in a controlled atmosphere tube furnace at temperatures between 500ºC and 1100ºC for 30 minutes. The photoluminescence spectra from the visible to the near-infrared region were acquired while pumping either near or far from the Er3+ absorption lines. Under both excitation conditions all samples annealed at temperatures below 1000ºC show clear emission at 1.535μm from Er3+ ions in the host material. In the current literature this is attributed to exciton mediated excitation of the Er3+. By contrast, in these studies indirect excitation was observed for samples annealed at temperatures well below the onset of nanocrystal nucleation and growth (between 500ºC and 1000ºC), suggesting excitation via small clusters or lattice defects. These findings could have significant implications in the further development of group IV sensitized silicon compatible gain media.M.S.
Other
Optics and Photonics
Optics
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Kaleli, Buket. "Towards Silicon Based Light Emitting Devices: Photoluminescence From Terbium Doped Silicon Matrices With Or Without Nanocrystals." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610614/index.pdf.
Full textAbstract:
In this study, silicon (Si) rich silicon dioxide (SiO2) films and terbium (Tb) embedded in three different Si containing films has been produced by e-beam evaporation and magnetron sputtering techniques. Post deposition annealing was done for different temperatures and durations to study its effect on both Si nanocrystal formation and Tb luminescence. It was verified by X-ray diffraction technique (XRD) that Si nanocrystals were formed in Si rich matrices. Energy dispersive X-ray (EDS) spectroscopy analysis was carried out to determine the relative concentrations of the atoms inside the produced films. X-ray photoelectron spectroscopy (XPS) gave the evidence of different bonding structures inside the Tb-Si-O containing films. Depth profile measurements were carried out to analyze changes in the relative concentration during sputtering of the layers after annealing of the Tb containing film. Luminescence characteristics of Si nanocrystals and Tb3+ ions were studied by photoluminescence (PL) spectroscopy. It was observed that Tb3+ luminescence enhanced by an energy transfer from Si nanocrystals and trap levels in a matrix. This result supplies valuable information about the excitation paths of Tb3+ ion the way of intense luminescence.
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Wilkinson, Andrew Richard, and arw109@rsphysse anu edu au. "The Optical Properties of Silicon Nanocrystals and the Role of Hydrogen Passivation." The Australian National University. Research School of Physical Sciences and Engineering, 2006. http://thesis.anu.edu.au./public/adt-ANU20060202.111537.
Full textAbstract:
This thesis examines the optical properties of nanoscale silicon and the sensitization of Er with Si. In this context, it predominantly investigates the role of defects in limiting the luminescence of Si nanocrystals, and the removal of these defects by hydrogen passivation. The kinetics of the defect passivation process, for both molecular and atomic hydrogen, are studied in detail. Moreover, the optical absorption of Si nanocrystals and the effect of annealing environment (during nanocrystal synthesis) on the luminescence are investigated. The effect of annealing temperature and hydrogen passivation on the coupling (energy transfer) of Si nanocrystals to optically active centres (Er) is also examined.¶
The electronic structure of silicon-implanted silica slides is investigated through optical absorption measurements. Before and after annealing to form Si nanocrystals, optical absorption spectra from these samples show considerable structure that is characteristic of the particular implant fluence. This structure is shown to correlate with the transmittance of the samples as calculated from the modified refractive index profile for each implant. Due to the high absorption coefficient of Si at short wavelengths, extinction at these wavelengths is found to be dominated by absorption. As such, scattering losses are surprisingly insignificant.
To eliminate interference effects, photothermal deflection spectroscopy is used to obtain data on the band structure of Si in these samples. This data shows little variance from bulk Si
structure and thus little effect of quantum confinement. This is attributed to the dominance of
large nanocrystals in the absorption measurements.¶
The effect of annealing environment on the photoluminescence (PL) from silicon nanocrystals synthesized in fused silica by ion implantation and thermal annealing is studied as a function of annealing temperature and time. Interestingly, the choice of annealing environment (Ar, N2, or 5 % H2 in N2) is found to affect the shape and intensity of luminescence emission
spectra, an effect that is attributed both to variations in nanocrystal size and the density of defect states at the nanocrystal/oxide interface.¶
The passivation kinetics of luminescence-quenching defects, associated with Si nanocrystals in SiO2, during isothermal and isochronal annealing in molecular hydrogen are studied by time-resolved PL. The passivation of these defects is modeled using the Generalized Simple
Thermal model of simultaneous passivation and desorption, proposed by Stesmans. Values for the reaction-rate parameters are determined for the first time and found to be in excellent
agreement with values previously determined for paramagnetic Si dangling-bond defects (Pb type centers) found at planar Si/SiO2 interfaces; supporting the view that non-radiative recombination in Si nanocrystals is dominated by such defects.¶
The passivation kinetics of luminescence-quenching defects during isothermal and isochronal annealing in atomic hydrogen are studied by continuous and time-resolved PL. The kinetics are compared to those for standard passivation in molecular hydrogen and found to be
significantly different. Atomic hydrogen is generated using the alneal process, through reactions between a deposited Al layer and H2O or OH radicals in the SiO2. The passivation and desorption kinetics are shown to be consistent with the existence of two classes of nonradiative defects: one that reacts with both atomic and molecular hydrogen, and the other that reacts only with atomic hydrogen. A model incorporating a Gaussian spread in activation energies is presented that adequately describes the kinetics of atomic hydrogen passivation and dissociation for the samples.¶
The effect of annealing temperature and hydrogen passivation on the excitation cross-section and PL of erbium in silicon-rich silica is studied. Samples are prepared by co-implantation of Si and Er into SiO2 followed by a single thermal anneal at temperatures ranging from 800 to
1100 degrees C, and with or without hydrogen passivation performed at 500 degrees C. Using time-resolved PL, the effective erbium excitation cross-section is shown to increase by a factor of 3, while the number of optically active erbium ions decreases by a factor of 4 with increasing annealing temperature. Hydrogen passivation is shown to increase the luminescence intensity
and to shorten the luminescence lifetime at 1.54 micron only in the presence of Si nanocrystals. The implications of these results for realizing a silicon-based optical amplifier are also discussed.
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Kulakci, Mustafa. "Silicon Nanocrystals Embedded In Sio2 For Light Emitting Diode (led) Applications." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606557/index.pdf.
Full textAbstract:
In this study, silicon nanocrystals (NC) were synthesized in silicon dioxide matrix by ion implantation followed by high temperature annealing. Annealing temperature and duration were varied to study their effect on the nanocrystal formation and optical properties. Implantation of silicon ions was performed with different energy and dose depending on the oxide thickness on the silicon substrate. Before device fabrication, photoluminescence (PL) measurement was performed for each sample. From PL measurement it was observed that, PL emission depends on nanocrystal size determined by the parameters of implantation and annealing process. The peak position of PL emission was found to shifts toward higher wavelength when the dose of implanted Si increased. Two PL emission bands were observed in most cases. PL emission around 800 nm originated from Si NC in oxide matrix. Other emissions can be attributed to the luminescent defects in oxide or oxide/NC interface.
In order to see electroluminescence properties Light Emitting Devices (LED) were fabricated by using metal oxide semiconductor structure, current-voltage (I-V) and electroluminescence (EL) measurements were conducted. I-V results revealed that, current passing through device depends on both implanted Si dose and annealing parameters. Current increases with increasing dose as one might expect due to the increased amount of defects in the matrix. The current however decreases with increasing annealing temperature and duration, which imply that, NC in oxide behave like a well controlled trap level for charge transport. From EL measurements, few differences were observed between EL and PL results. These differences can be attributed to the different excitation and emission mechanisms in PL and EL process. Upon comparision, EL emission was found to be inefficient due to the asymmetric charge injection from substrate and top contact. Peak position of EL emission was blue shifted with respect to PL one, and approached towards PL peak position as applied voltage increased. From the results of the EL measurements, EL emission mechanisms was attributed to tunneling of electron hole pairs from top contact and substrate to NC via oxide barrier.
30
Von, Treskow Carl. "Unaltered Blinking in Single Silicon Oxidized Nanocrystals when X-ray Irradiated." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201713.
Full textAbstract:
Quantum dots exhibit a range of interesting and useful properties linked to their elemental composition, crystal structure, size and shape. Two such properties is the work function and blinking frequency. Tests on several different quantum dot types have shown that x-ray radiation will alter these factors; with increasing doses "bleaching" the dots and making them permanently dark. There are several competing theories to explain this behavior and a lot of materials systems that have not been investigated yet. One such unexplored material is oxidized silicon NCs. This work found no consistent change in work function or blinking frequency after an X-ray dose of ~272 000 Gy absorbed by the SiO2. Individual dots changed between PL measurements but as a whole the sample remained statistically unchanged.
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Locritani, Mirko <1983>. "Development of synthetic methods of silicon nanocrystals functionalized with photoactive molecules." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7016/1/Locritani_Mirko_tesi.pdf.
Full textAbstract:
The thesis is focused on the development of a method for the synthesis of silicon nanocrystals with different sizes, narrow size distribution, good optical properties and stability in air.
The resulting silicon nanocrystals have been covalently functionalized with different chromophores with the aim to exploit the new electronic and chemical properties that emerge from the interaction between silicon nanocrystal surface and ligands.
The purpose is to use these chromophores as light harvesting antennae, increasing the optical absorption of silicon nanocrystals.
Functionalized silicon nanocrystals have been characterized with different analytical techniques leading to a good knowledge of optical properties of semiconductor quantum dots.
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Locritani, Mirko <1983>. "Development of synthetic methods of silicon nanocrystals functionalized with photoactive molecules." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7016/.
Full textAbstract:
The thesis is focused on the development of a method for the synthesis of silicon nanocrystals with different sizes, narrow size distribution, good optical properties and stability in air.
The resulting silicon nanocrystals have been covalently functionalized with different chromophores with the aim to exploit the new electronic and chemical properties that emerge from the interaction between silicon nanocrystal surface and ligands.
The purpose is to use these chromophores as light harvesting antennae, increasing the optical absorption of silicon nanocrystals.
Functionalized silicon nanocrystals have been characterized with different analytical techniques leading to a good knowledge of optical properties of semiconductor quantum dots.
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Tengattini, Andrea. "Erbium and Silicon Nanocrystals based Light Emitting Devices for lightwave circuits." Doctoral thesis, Università degli studi di Trento, 2013. https://hdl.handle.net/11572/368417.
Full textAbstract:
The thesis is divided into two topics: silicon nanocrystals based light emitting devices and erbium doped silicon nanocrystals devices. I have studied silicon nanocrystals based devices. Here I have demonstrated the role of the different injection mechanisms in determining the efficiency of the device. I have studied single and multilayer structures, both in diode or transistor configurations. Lastly, the time dependence of the electroluminescence has been studied, clarifying the role of bipolar or unipolar injection in these structures.
On the second part of my thesis, I have studied Er and silicon nanocrystals co-doped devices. Firstly, the study was aimed at the understanding of the efficiency of the electrical pumping of Er ions. Then, integrated optical cavities were designed and fabricated and their optoelectronic properties measured. Here I built a specific set-up in order to measure at the same time the optical and electronic properties of active devices on wafer. Unfortunately, the measurements demonstrated that many nonlinear loss mechanisms set in when the devices are heavily injected with current. Therefore, despite the optical cavities are of high qualities, the system did not show any laser emission. On the other hand, I have demonstrated a fully integrated system where the Er doped injection device pumps a waveguide and the emission is then extracted through a grating. Last result was the experimental verification of the existence of intermediate band states through which the silicon nanocrystals to Er energy transfer occurs.
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Tengattini, Andrea. "Erbium and Silicon Nanocrystals based Light Emitting Devices for lightwave circuits." Doctoral thesis, University of Trento, 2013. http://eprints-phd.biblio.unitn.it/1091/1/PhD_Thesis_Andrea_Tengattini.pdf.
Full textAbstract:
The thesis is divided into two topics: silicon nanocrystals based light emitting devices and erbium doped silicon nanocrystals devices. I have studied silicon nanocrystals based devices. Here I have demonstrated the role of the different injection mechanisms in determining the efficiency of the device. I have studied single and multilayer structures, both in diode or transistor configurations. Lastly, the time dependence of the electroluminescence has been studied, clarifying the role of bipolar or unipolar injection in these structures.
On the second part of my thesis, I have studied Er and silicon nanocrystals co-doped devices. Firstly, the study was aimed at the understanding of the efficiency of the electrical pumping of Er ions. Then, integrated optical cavities were designed and fabricated and their optoelectronic properties measured. Here I built a specific set-up in order to measure at the same time the optical and electronic properties of active devices on wafer. Unfortunately, the measurements demonstrated that many nonlinear loss mechanisms set in when the devices are heavily injected with current. Therefore, despite the optical cavities are of high qualities, the system did not show any laser emission. On the other hand, I have demonstrated a fully integrated system where the Er doped injection device pumps a waveguide and the emission is then extracted through a grating. Last result was the experimental verification of the existence of intermediate band states through which the silicon nanocrystals to Er energy transfer occurs.
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Spooner, Marc, and mas109@rsphysse anu edu au. "The Application and Limitations of PECVD for Silicon-based Photonics." The Australian National University. Research School of Physical Sciences and Engineering, 2006. http://thesis.anu.edu.au./public/adt-ANU20070315.043442.
Full textAbstract:
This thesis presents results on the applications and limitations of plasma enhanced chemical vapour deposition for silicon-based photonics, with an emphasis on optical microcavities for the control of light emission from silicon nanocrystals.
¶
Silicon nanocrystals were formed by precipitation and growth within Si-rich oxide layers (SiOx) deposited by plasma enhanced chemical vapour deposition. The films were found to exhibit strong room temperature photoluminescence, with the optimum emission depending
on the composition and processing of the films. The strongest emission was achieved for films with a silicon content of ~40%, following hydrogen passivation. Hydrogen was introduced into the samples by two different methods: by annealing in forming gas (95% N2: 5% H2) or by annealing with a hydrogenated silicon nitride capping layer. Both methods caused an increase in photoluminescence intensity due to the passivation of defects. In contrast, the presence of low levels of iron and gold were shown to reduce the concentration of luminescent nanocrystals due to the creation of non-radiative centres.
¶
Optical microcavity structures containing silicon nanocrystals were also fabricated by Plasma enhanced chemical vapour deposition, using silicon dioxide, silicon nitride and silicon-rich oxide layers. The microcavities consisted of a silicon-rich oxide layer between two distributed Bragg reflectors formed of alternating silicon dioxide/nitride layers. The optical emission from these and related structures were examined and compared with that from individual layers in the structure. This revealed a complex interplay between defect and nanocrystal luminescence, hydrogen passivation and materials structure. The resulting microcavity structures were shown to be suitable for producing a stop-band over the wavelength range of interest for nanocrystal emission, 500-1000nm, and to produce significant intensity enhancement and spectral narrowing. Quality factors of 50-200 were demonstrated.
¶
The application of plasma deposited films was shown to be limited by stress-induced failure that resulted in cracking and delamination of the films during annealing. The SiOx films thicker than about 600nm failed predominantly by cracking. This was shown to be caused by tensile stress in the film caused by hydrogen desorption during high temperature annealing. The resulting cracks showed preferred alignment depending on the crystallographic orientation of the silicon substrate. For films deposited on (100) silicon, two modes of crack propagation were observed, straight cracks aligned along < 100> directions, and wavy cracks aligned along < 110> directions. For films deposited on (110) silicon, straight cracks were observed along [-1 10] directions, with a lesser number aligned along [001] directions. Cracks were also observed for films on (111) silicon. These showed
3-fold symmetry consistent with crack propagation along < 211> directions due to plastic deformation. Details of these crack geometries and their dependencies are discussed.
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Seregin, Vladimir Victor. "Part I, Fabrication and surface modification of composite biomaterials based on silicon and calcium disilicide Part II, Synthesis and characterization of erbium doped silicon nanocrystals encapsulated by aluminum and zinc oxides /." Fort Worth, Tex. : Texas Christian University, 2006. http://etd.tcu.edu/etdfiles/available/etd-04252006-145309/unrestricted/seregin.pdf.
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Mitra, Somak. "Nanoscale engineering for the integration of silicon nanocrystals in solar cells nanoarchitectures." Thesis, Ulster University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629076.
Full textAbstract:
One of the main contributions of this thesis is the improvement on the overall performance of the solar cells due to the impact of the surface engineering of silicon nanocrystals (SiNCs) and also down conversion of high energy photons by SiNCs. It is demonstrated that surface engineering techniques by using microplasma processing improve the capabilities of the SiNCs for different opto-electronic applications and in particular for solar cells. Surface engineering of SiNCs in water shows long term stability, which could allow the deployment of SiNCs for a wider range of applications. Microplasma-induce liquid chemistry on SiNCs in ethanol and water shows very unique surface properties which are not achievable by other techniques. The optical and electronic properties of SiNCs/polymer colloid and nanocomposites have been analyzed. It has been found that microplasma processed SiNCs/polymer nanocomposite shows improved optical properties and also exhibits enhanced photogeneration and conductivity. This thesis is focused on the application of SiNCs in photovoltaic devices. Hybrid bulk heterojunction solar cells and SiNCs-Schottkey barrier photo voltaic devices have been developed. Hybrid bulk heterojunction solar cells have polymers and SiNCs as an active layer. A range of different device structures have been produced and investigated with support from current-voltage characteristics, which contributed to identify band alignment and the suitability of the architectures for the solar cells. The results also explain the limitations of the solar cells due to either dissociation and/or transport properties. SiNCs based nanocomposites are being employed as an optical converter first time in organic solar cell. SiNCs/polymer nanocomposite allows down conversion of high energy photons demonstrating a drastic improvement in solar cell efficiency with concentrated light.
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Khavari, Faraz. "Towards monodisperse Silicon Nanocrystals: density gradient centrifugation applied on commercial gold nanoparticles." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-186172.
Full textAbstract:
The application of silicon nanocrystals as non-toxic bio-labels and downconverters requires their uniform size distribution in order to minimize the inhomogeneous broadening of the photoluminescence peak. In this thesis, we set the basis for their size-separation via the density-gradient centrifugation method. To be more precise, we successfully apply this technique to separate 5 and 10 nm gold nanoparticles from an ensemble by using an engineered medium layer stack. In addition, we explain how atomic force microscopy is used to measure the size of the nanoparticles, with a particular attentionon the removal of unwanted solvent-related effects. As a future plan, we will implement the technique for the size-separation of silicon nanocrystals.
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Spooner, Marc. "The application and limitations of PECVD for silicon-based photonics /." View thesis entry in Australian Digital Program, 2005. http://thesis.anu.edu.au/public/adt-ANU20070315.043442/index.html.
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Alsharif, Naif Hazza S. "In vitro application of alkyl-capped silicon nanocrystals for investigation of cell behavior." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525064.
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Seyhan, Ayse. "Photoluminescence Properties Of Si Nanocrystals Embedded In Sio2 Matrix." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611750/index.pdf.
Full textAbstract:
This thesis examines the luminescence properties of nanoscale silicon (Si) by
using spectroscopic techniques. Since the development of new optical devices
requires understanding light emission mechanism optical spectroscopy has
become more important tool in the analysis of these structures. In this thesis, Si
nanocrystals embedded in SiO2 matrix will be studied.
Photoluminescence (PL) and Time-resolved photoluminescence spectroscopy
(TRPL) have been used to detect the light emission in UV-Vis-NIR range.
Experiments have been performed in the temperature range 10-300 K. PL is
sensitive to impurities and defects that affect materials quality and device
performance. In this context, the role of defects in limiting the luminescence of Si
nanocrystals and the removal of these defects by hydrogen passivation has been
investigated.
v
TRPL was employed to determine the time evolution of photoluminescence as
function of temperature. The decay time of the PL spectra was determined by a
stretched exponential function and perfectly fitted to an expression based on three
excitonic levels. Carrier lifetimes associated with these three levels were
determined and compared with literature.
Additionally, temporal variation of PL from free-standing Si nanoparticles is
studied under a strong laser illumination. The observed bleaching behavior (time
dependent emission intensity), which is reversible, have discussed in terms of
exciton trapping at the interface between nanocrystal and the surrounding oxide
layer.
The results of this thesis will provide new insight on the understanding of light
emission mechanism of Si nanocrytals.
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Danko, V. A., P. E. Shepeliavyi, K. V. Michailovska, and I. Z. Indutnyi. "Absorption Cross Section and Photoluminescence Lifetime of Silicon-Based Light-Emitting nc-Si-SiOx Structures." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35011.
Full textAbstract:
The spectral dependence of the photoluminescence (PL) decay kinetics at room temperature have been
studied in porous nc-Si-SiOx nanostructures. Investigated samples were obtained by oblique evaporation of
SiO with following annealing at 975 C in vacuum and treating in the HF vapor at 50 C. PL decay in these
structures described by a stretched exponential and the average lifetime of the PL decrease exponentially
with increasing energy of photons. PL lifetime values is in microsecond range that point out on phonon
participation in radiative recombination. Dispersion parameter do not depend on emission energy and
tends to 1 with increasing porosity, which is consistent with the model of noninteracting nc-Si. It was established,
that the absorption cross section σ of the nc-Si particles increase with decreasing of nc-Si dimensions
and increasing of emission energy.
This result is consistent with the quantum confinement effects, where the smaller nc-Si with larger
energy gaps are characterized by a short radiative lifetime and the corresponding radiative recombination
process take place within the individual nc-Si.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35011
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Vlasukova, L., F. Komarov, O. Milchanin, I. Parkhomenko, and J. Zuk. "Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35436.
Full textAbstract:
We reported the structure peculiarities of nanocrystals formed in Si by means of high-fluence implantation
at 25 and 500 °С followed by rapid thermal annealing (RTA). The structure of implanted samples
has been investigated by means of transmission electron microscopy (TEM). The crystalline nature of the
precipitates is proved by the Moiré fringe patterns presence in the TEM images. The Moiré fringe distance
(Moiré period) is equal of 1.8 nm for small precipitates. This experimental value coincides with the calculated
one for crystalline InAs. It is noted a Moiré period increasing in the case of large precipitates. We
suppose that this feature is a result of surplus As or In atoms embedded in precipitates. One can see an interesting
effect – “glowng” of nanocrystal/Si interfaces at the dark-field images of implanted and annealed
samples. We ascribe this effect to a presence of misfit dislocation networks at the InAs/Si interfaces generated
as a result of strain relaxation in highly mismatched InAs/Si system.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35436
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Beri, Deski [Verfasser], and F. [Akademischer Betreuer] Breitling. "Surface functionalization of silicon nanocrystals via a microwave reactor / Deski Beri ; Betreuer: F. Breitling." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1225401216/34.
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Morselli, Giacomo <1994>. "Synthesis and electronic properties of luminescent silicon nanocrystals and copper indium sulphide quantum dots." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10175/1/Thesis_Morselli%20G.pdf.
Full textAbstract:
In the last decades, nanomaterials, and in particular semiconducting nanoparticles (or quantum dots), have gained increasing attention due to their controllable optical properties and potential applications.
Silicon nanoparticles (also called silicon nanocrystals, SiNCs) have been extensively studied in the last years, due to their physical and chemical properties which render them a valid alternative to conventional quantum dots. During my PhD studies I have planned new synthetical routes to obtain SiNCs functionalised with molecules which could ameliorate the properties of the nanoparticle. However, this was certainly challenging, because SiNCs are very susceptible to many reagents and conditions that are often used in organic synthesis. They can be irreversibly quenched in the presence of alkalis, they can be damaged in the presence of oxidants, they can modify their optical properties in the presence of many nitrogen-containing compounds, metal complexes or simple organic molecules. If their surface is not well-passivated, the oxygen can introduce defect states, or they can aggregate and precipitate in several solvents.
Therefore, I was able to functionalise SiNCs with different ligands: chromophores, amines, carboxylic acids, poly(ethylene)glycol, even ameliorating functionalisation strategies that already existed.
This thesis will collect the experimental procedures used to synthesize silicon nanocrystals, the strategies adopted to functionalise effectively the nanoparticle with different types of organic molecules, and the characterisation of their surface, physical properties and luminescence (mostly photogenerated, but also electrochemigenerated).
I also spent a period of 7 months in Leeds (UK), where I managed to learn how to synthesize other cadmium-free quantum dots made of copper, indium and sulphur (CIS QDs). During my last year of PhD, I focused on their functionalisation by ligand exchange techniques, yielding the first example of light-harvesting antenna based on those quantum dots. Part of this thesis is dedicated to them.
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Smith, Kristen Colleen. "Surface processes ruthenium film growth, silicon nanocrystal synthesis, and methylene partial oxidation /." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035980.
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Greben, M. V., F. F. Komarov, L. A. Vlasukova1, O. V. Milchanin, A. V. Mudryi, and I. N. Parkhomenko. "The Comparative Investigations of Structural and Optical Properties of GaSb nanocrystals / Si layers." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35169.
Full textAbstract:
Optical and structural properties of GaSb nanocrystals fabricated by co-implantation of Ga and Sb ions
in single crystalline Si (100), followed by thermal treatment are investigated. In the first group of samples
named Si / GaSb the implantation of Ga ions was followed by Sb implantation, whereas in the second
group of samples named Si / SbGa with increased by factor 1.4 ion fluence the order of implantation was
inverted. The presence of nanocrystals in both kinds of samples was proved by TEM and RS experiments.
Low-temperature PL measurements show a PL broad band in the region at 0.75-1.1 eV for Si / SbGa samples
annealed at 900 °C. No PL was observed in the Si/SbGa samples after annealing at 1100 °C.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35169
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Abualnaja, Khamael. "An investigation of the effect of metal nanoparticles on the optical properties of silicon nanocrystals." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/3108.
Full textAbstract:
This thesis describes the characterization of two types of nanocrystalline material i.e. alkylated silicon nanocrystals (C11-SiNCs) and commercial silicon nanocrystals (SiNCs). The research presented throughout this work also shows that the optical properties of silicon nanocrystals can be affected by erbium ions and metal nanoparticles. The main goal of this characterization is to observe the energy transfer from the excited state of SiNCs to the erbium for optical fiber technology applications. Also, SiNCs have applications in biology as fluorescent labels. Porous silicon was prepared successfully by galvanostatic etching of p-Si(100) wafers followed by a thermal hydrosilation reaction of 1-undecene in refluxing toluene in order to extract the C11-SiNCs from porous silicon. The chemical characterization of C11-SiNCs was carried out using X-ray photoemission spectroscopy (XPS); they are known to be crystalline and of diameter about 5 nm from previous work. The commercial SiNCs have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Atomic force microscopy (AFM), X-ray diffraction (XRD), XPS and Fourier transform infrared spectroscopy (FTIR). It was found that the average diameter of commercial SiNCs is 65 nm and are crystalline with an FCC lattice. Erbium trichloride was added to both types of SiNCs using a simple mixing chemical route. To the best of our knowledge, this is the first investigation on mixing SiNCs with erbium ions (III) by this chemical method. Both SiNCs either C11-SiNCs or commercial SiNCs and their mixtures with Er3+ were investigated using Raman spectroscopy and photoluminescence (PL). The samples showed an orange PL emission peak at around 595 nm which originates from Si. Er/SiNCs mixtures also exhibit a weak PL emission peak at 1536 nm which originates from the intra-4f transition in erbium ions (Er3+). The PL peak of Si in Er/C11-SiNCs and Er/Commercial SiNCs mixtures are increased in the intensity up to four and three times, respectively as compared to pure C11-SiNCs and commercial SiNCs. The collected data suggest that this chemical mixing route leads instead to a transfer of energy from erbium ions to SiNCs. Metal-enhanced luminescence has been studied for mixtures of SiNCs (either C11-SiNCs or commercial SiNCs) with silver nanoparticles (AgNPs). AgNPs of two different sizes were synthesised using photochemical reduction of AgNO3 with sodium dodecyl sulphate (SDS). The synthesized AgNPs (1:5) and (10:50) have a polycrystalline structure with an average particle diameter of 100 nm and 30 nm, respectively. A significant enhancement up to 10 and 4 times in the PL intensity was observed for AgNPs (1:5)/C11-SiNCs and AgNPs (10:50)/C11-SiNCs, respectively using an excitation source of 488 nm. A similar observation was also reported for AgNPs (1:5)/Commercial SiNCs and AgNPs (10:50)/Commercial SiNCs; where the intensity of the PL signal increased up to 9 and 3 times respectively, using 488 nm; whereas the intensity of the PL signal increased up to 7 and 2 times respectively, using 514.5 nm excitation source. The enhancement in SERS intensities occurs as a result of the coupling between the excitation laser light and the plasmon bands of AgNPs; thus this intense field at AgNPs surface couples strongly to SiNCs. The results show that the closer wavelength of the laser excitation source to the surface plasmon resonance absorption bands of silver nanoparticles the greater the emission intensity. Our study also suggests that the larger AgNPs (1:5) caused an optimum enhancement in PL intensity of both types of SiNCs. Under continuous wave (CW) irradiation at 488 nm in a confocal microscope, both types of SiNCs show reversible photoluminescence fading behaviour. This can be interpreted by the same model originally proposed to describe luminescence intermittency, i.e., ’blinking’. When single particles are studied, this leads to the wellknown blinking phenomenon as particles ionize and later discharge by electron-hole recombination. In an ensemble, the result is a reversible photofading as the initial photoluminescence I₀ decays to a steady-state I∞ controlled by the relative rates of photoionization ka and recombination keh. Evidence for this interpretation comes from two observations: (i) upon cessation of the irradiation, electron-hole recombination occurs in the dark and the photoluminescence is regained when irradiation recommences and (ii) the initial and steady-state spectra are identical except for a scale factor. The photofading data can be modelled as a simple first order decay with a lognormal distribution of rate constants and therefore characterized by three parameters; {k} the modal rate constant, γ which measures the spread of activiation free energies in units of RT and I₀/I∞. C11-SiNCs and commercial SiNCs show enhanced luminescence when drop cast as films on glass slides in mixtures with Ag or Au nanoparticles. Such metal-enhanced luminescence is generally explained in terms of the large electric field near the metal surface upon excitation of the plasmon resonance and an increase in the radiative decay rate owing to the effect of the plasmon on the optical density of states. In this work, we find evidence for a third effect: the metal nanoparticles can act as a source of electrons and increase the time integrated luminescence intensity by increasing the rate of electron-hole recombination. In the presence of Ag and Au nanoparticles with alkyl-capped SiNCs, the modal rate constants {k} increase by factors of up to 4-fold and the ratios I₀/I∞ decrease by factors up to 5-fold; this is consistent with an increase in the rate of electron-hole recombination facilitated by the metal nanoparticles acting as a source of electrons. It is also should be noted that the presence of either Ag or Au NPs with commercial SiNCs are less effective at enhancing the PL than alkyl-capped SiNCs due to the larger average particle size of commercial SiNCs.
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Pinto, Emilio Sergio Marins Vieira. "Sintese e caracterização de nanocristais de Ge por LPCVD." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259199.
Full textAbstract:
Orientador: Ioshiaki DoiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Nesta dissertação estudamos a obtenção de nanocristais (NCs) de Ge pela técnica de LPCVD (Low Pressure Chemical Vapor Deposition), buscando otimizar as condições de processo que resultassem em NCs com características de tamanho, densidade por unidade de área e uniformidade de tamanhos, que são necessárias para aplicação em dispositivos de memórias de porta flutuante. Os NCs foram fabricados por processo de dois passos: 1) formação de núcleos de Si na superfície do SiO2, a partir de silana (SiH4); 2) crescimento de Ge sobre os núcleos de Si através de deposição de germana (GeH4). Realizamos ciclos de deposição e caracterização das amostras, e os parâmetros de processo: temperatura, pressão total, fluxos de silana e germana e tempo de deposição, foram alterados convenientemente, com base na literatura e nos resultados obtidos a cada ciclo de fabricação. As amostras foram caracterizadas quanto à morfologia, por microscopia de força atômica (AFM) e a estrutura dos NCs foi analisada por microscopia eletrônica de transmissão de alta resolução (HRTEM). Estudamos a influência dos parâmetros de processo nas características dos NCs e observamos tendências de aumento da densidade de NCs com a elevação da temperatura, pressão total e fluxo de SiH4 do passo 1. E, o tamanho dos NCs tendem a diminuir com a redução da temperatura, pressão total e tempo de deposição do passo 2. Os resultados mostram que com os parâmetros: 600 ºC / 5 Torr / 20 sccm de SiH4 / 20 seg. para a nucleação de Si e 550 ºC / 2 Torr / 5 sccm / 30 seg. para a deposição de Ge, é possível obter alta densidade de NCs por unidade área de 4x1010 NCs/cm2 com diâmetro médio de 19 nm e altura média de 4,5 nm
Abstract: In this thesis we studied the synthesis of Ge nanocrystals (NCs) by the LPCVD technique (Low Pressure Chemical Vapor Deposition). We looked for NCs with characteristics of sizes, density and uniformity of sizes that are necessary for applications in floating gate memory devices. To reach those characteristics we have optimized the process conditions. The NCs were fabricated by a process of two steps: 1) formation of Si nuclei on SiO2 surface, through the silane (SiH4) decomposition; 2) Ge growth on Si nuclei through germane (GeH4) deposition. We accomplished deposition cycles and characterization of the samples. The process parameters: temperature, total pressure, silana and germana flow and deposition time, were altered conveniently based on the literature and results obtained at each production cycle. The morphology of the samples was analyzed by atomic force microscopy (AFM) and the NCs structures were analyzed by high resolution transmission electron microscopy (HRTEM). We studied the influence of the process parameters in the NCs characteristics and we have observed tendencies of NCs density increase with rise of the temperature, total pressure and SiH4 flow of step 1. The NCs size tends to decrease with the reduction of temperature, total pressure and deposition time of step 2. The results show that with the parameters: 600 ºC / 5 Torr / 20 sccm de SiH4 / 20 sec. for the Si nucleation and 550 ºC / 2 Torr / 5 sccm / 30 sec. for the Ge deposition, it¿s possible to reach a high density of NCs (4x1010 NCs/cm2) with diameter of 19 nm and average height of 4,5 nm
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Wutzler, René. "Integration of III-V compound nanocrystals in silicon via ion beam implantation and flash lamp annealing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-231433.
Full textAbstract:
The progress in device performance of modern microelectronic technology is mainly driven by down-scaling. In the near future, this road will probably reach a point where physical limits make even more down-scaling impossible. The substitution of single components materialwise over the last decades, like high-k dielectrics or metal gates, has been a suitable approach to foster performance improvements. In this scheme, the integration of high-mobility III-V compound semiconductors as channel materials into Si technology is a promising route to follow for the next one or two device generations. III-V integration, today, is conventionally performed by using techniques like molecular beam epitaxy or wafer bonding which utilize solid phase crystallization but suffer to strain due to the lattice mismatch between III-V compounds and Si. An alternative approach using sequential ion beam implantation in combination with a subsequent flash lamp annealing is presented in this work. Using this technique, nanocrystals from various III-V compounds have been successfully integrated into bulk Si and Ge as well as into thin Si layers which used either SOI substrates or were grown by plasma-enhanced chemical vapour deposition. The III-V compounds which have been fabricated are GaP, GaAs, GaSb, InP, InAs, GaSb and InxGa1-xAs with variable composition. The structural properties of these nanocrystals have been investigated by Rutherford backscattering, scanning electron microscopy and transmission electron microscopy, including bright-field, dark-field, high-resolution, high-angle annular dark-field and scanning mode imaging, electron-dispersive x-ray spectroscopy and energy-filtered element mapping. Furthermore, Raman spectroscopy and X-ray diffraction have been performed to characterise the nanocrystals optically. In Raman spectroscopy, the characteristic transversal and longitudinal optical phonon modes of the different III-V compounds have been observed. These signals proof that the nanocrystals have formed by the combination of ion implantation and flash lamp annealing. Additionally, the appearance of the typical phonon modes of the respective substrate materials verifies recrystallization of the substrate by the flash lamp after amorphisation during implantation. In the bulk Si samples, the nanocrystals have a circular or rectangular lateral shape and they are randomly distributed at the surface. Their cross-section has either a hemispherical or triangular shape. In bulk Ge, there are two types of precipitates: one at the surface with arbitrary shape and another one buried with circular shape. For the thin film samples, the lateral shape of the nanocrystals is more or less arbitrary and they feature a block-like cross-section which is limited in height by the Si layer thickness. Regarding crystalline quality, the nanocrystals in all samples are mainly single-crystalline with only a few number of stacking faults. However, the crystalline quality in the bulk samples is slightly better than in the thin films. The X-ray diffraction measurements display the (111), (220) and (311) Bragg peaks for InAs and GaAs as well as for the InxGa1-xAs where the peaks shift with increasing In content from GaAs towards InAs. The underlying formation mechanism is identified as liquid phase epitaxy. Hereby, the ion implantation leads to an amorphisation of the substrate material which is then molten by the subsequent flash lamp annealing. This yields a homogeneous distribution of the implanted elements within the melt due to their strongly increased diffusivity in the liquid phase. Afterwards, the substrate material starts to recrystallize at first and an enrichment of the melt with group-III and group-V elements takes place due to segregation. When the temperature is low enough, the III-V compound semiconductor starts to crystallize using the recrystallized substrate material as a template for epitaxial growth. In order to gain control over the lateral nanocrystal distribution, an implantation mask of either aluminium or nickel is introduced. Using this mask, only small areas of the samples are implanted. After flash lamp treatment, nanocrystals form only in these small areas, which allows precise positioning of them. An optimal implantation window size with an edge length of around 300nm has been determined to obtain one nanocrystal per implanted area. During an additional experiment, the preparation of Si nanowires using electron beam lithography and reactive ion etching has been conducted. Hereby, two different processes have been investigated; one using a ZEP resist, a lift-off step and a Ni hard mask and another one using a hydrogen silsesquioxane resist which is used directly as a mask for etching. The HSQ-based process turned out to yield Si nanowires of better quality. Combining both, the masked implantation and the Si nanowire fabrication, it might be possible to integrate a single III-V nanocrystal into a Si nanowire to produce a III-V-in-Si-nanowire structure for electrical testingDer Fortschritt in der Leistungsfähigkeit der Bauelemente moderner Mikroelektroniktechnologie wird hauptsächlich durch das Skalieren vorangetrieben. In naher Zukunft wird dieser Weg wahrscheinlich einen Punkt erreichen, an dem physikalische Grenzen weiteres Herunterskalieren unmöglich machen. Der Austausch einzelner Teile auf Materialebene, wie Hoch-Epsilon-Dielektrika oder Metall-Gate-Elektroden, war während der letzten Jahrzehnte ein geeigneter Ansatz, um die Leistungsverbesserung voranzubringen. Nach diesem Schema ist die Integration von III-V-Verbindungshalbleiter mit hoher Mobilität ein vielversprechender Weg, dem man für die nächsten ein oder zwei Bauelementgenerationen folgen kann. Heutzutage erfolgt die III-V-Integration konventionell mit Verfahren wie der Molekularstrahlepitaxie oder dem Waferbonden, welche die Festphasenkristallisation nutzen, die aber aufgrund der Gitterfehlanpassung zwischen III-V-Verbindungen und Silizium an Verspannungen leiden. In dieser Arbeit wird ein alternativer Ansatz präsentiert, welcher die sequenzielle Ionenstrahlimplantation in Verbindung mit einer darauffolgenden Blitzlampentemperung ausnutzt. Mit Hilfe dieses Verfahrens wurden Nanokristalle verschiedener III-V-Verbindungshalbleiter erfolgreich in Bulksilizium- und -germaniumsubstrate sowie in dünne Siliziumschichten integriert. Für die dünnen Schichten wurden hierbei entweder SOI-Substrate verwendet oder sie wurden mittels plasmagestützer chemischer Gasphasenabscheidung gewachsen. Die hergestellten III-V-Verbindungen umfassen GaP, GaAs, GaSb, InP, InAs, InSb und InxGa1-xAs mit veränderbarer Zusammensetzung. Die strukturellen Eigenschaften dieser Nanokristalle wurden mit Rutherford-Rückstreu-Spektroskopie, Rasterelektronenmikroskopie und Transmissionselektronenmikroskopie untersucht. Bei der Transmissionelektronenmikroskopie wurden die Hellfeld-, Dunkelfeld-, hochauflösenden, “high-angle annular dark-field” und Rasteraufnahmemodi sowie die energiedispersive Röntgenspektroskopie und die energiegefilterte Elementabbildung eingesetzt. Darüber hinaus wurden Ramanspektroskopie- und Röntgenbeugungsmessungen durchgeführt, um die Nanokristalle optisch zu charakterisieren. Mittels Ramanspektroskopie wurden die charakteristischen transversal- und longitudinal-optischen Phononenmoden der verschiedenen III-V-Verbindungen beobachtet. Diese Signale beweisen, dass sich unter Verwendung der Kombination von Ionenstrahlimplantation und Blitzlampentemperung Nanokristalle bilden. Weiterhin zeigt das Vorhandensein der typischen Phononenmoden der jeweiligen Substratmaterialien, dass die Substrate aufgrund der Blitzlampentemperung rekristallisiert sind, nachdem sie durch Ionenimplantation amorphisiert wurden. In den Bulksiliziumproben besitzen die Nanokristalle eine kreisförmige oder rechteckige Kontur und sind in zufälliger Anordnung an der Oberfläche verteilt. Ihr Querschnitt zeigt entweder eine Halbkugel- oder dreieckige Form. Im Bulkgermanium gibt es zwei Arten von Ausscheidungen: eine mit willkürlicher Form an der Oberfläche und eine andere, vergrabene mit sphärischer Form. Betrachtet man die Proben mit den dünnen Schichten, ist die laterale Form der Nanokristalle mehr oder weniger willkürlich und sie zeigen einen blockähnlichen Querschnitt, welcher in der Höhe durch die Siliziumschichtdicke begrenzt ist. Bezüglich der Kristallqualität sind die Nanokristalle in allen Proben mehrheitlich einkristallin und weisen nur eine geringe Anzahl an Stapelfehlern auf. Jedoch ist die Kristallqualität in den Bulkmaterialien ein wenig besser als in den dünnen Schichten. Die Röntgenbeugungsmessungen zeigen die (111), (220) und (311) Bragg-Reflexe des InAs und GaAs sowie des InxGa1-xAs, wobei sich hier die Signalpositionen mit steigendem Gehalt an Indium von GaAs zu InAs verschieben. Als zugrundeliegender Bildungsmechanismus wurde die Flüssigphasenepitaxie identifiziert. Hierbei führt die Ionenstrahlimplantation zu einer Amorphisierung des Substratmaterials, welches dann durch die anschließende Blitzlampentemperung aufgeschmolzen wird. Daraus resultiert eine homogene Verteilung der implantierten Elemente in der Schmelze, da diese eine stark erhöhte Diffusivität in der flüssigen Phase aufweisen. Danach beginnt zuerst das Substratmaterial zu rekristallisieren und es kommt aufgrund von Segregationseffekten zu einer Anreicherung der Schmelze mit den Gruppe-III- und Gruppe-V-Elementen. Wenn die Temperatur niedrig genug ist, beginnt auch der III-V-Verbindungshalbleiter zu kristallisieren, wobei er das rekristallisierte Substratmaterial als Grundlage für ein epitaktisches Wachstum nutzt. In der Absicht Kontrolle über die laterale Verteilung der Nanokristalle zu erhalten, wurde eine Implantationsmaske aus Aluminium beziehungsweise Nickel eingeführt. Durch die Benutzung einer solchen Maske wurden nur kleine Bereiche der Proben implantiert. Nach der Blitzlampentemperung werden nur in diesen kleinen Bereichen Nanokristalle gebildet, was eine genaue Positionierung dieser erlaubt. Es wurde eine optimale Implantationsfenstergröße mit einer Kantenlänge von ungefähr 300 nm ermittelt, damit sich nur ein Nanokristall pro implantierten Bereich bildet. Während eines zusätzlichen Experiments wurde die Präparation von Siliziumnanodrähten mit Hilfe von Elektronenstrahllithografie und reaktivem Ionenätzen durchgeführt. Hierbei wurden zwei verschiedene Prozesse getestet: einer, welcher einen ZEP-Lack, einen Lift-off-Schritt und eine Nickelhartmaske nutzt, und ein anderer, welcher einen HSQ-Lack verwendet, der wiederum direkt als Maske für die Ätzung dient. Es stellte sich heraus, dass der HSQ-basierte Prozess Siliziumnanodrähte von höherer Qualität liefert. Kombiniert man beides, die maskierte Implantation und die Siliziumnanodrahtherstellung, miteinander, sollte es möglich sein, einzelne III-V-Nanokristalle in einen Siliziumnanodraht zu integrieren, um eine III-V-in-Siliziumnanodrahtstruktur zu fertigen, welche für elektrische Messungen geeignet ist