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Articoli di riviste sul tema "Electrical dopant activation"
1
Kennedy, Noel, Ray Duffy, Luke Eaton, Dan O’Connell, Scott Monaghan, Shane Garvey, James Connolly, Chris Hatem, Justin D. Holmes e Brenda Long. "Phosphorus monolayer doping (MLD) of silicon on insulator (SOI) substrates". Beilstein Journal of Nanotechnology 9 (6 agosto 2018): 2106–13. http://dx.doi.org/10.3762/bjnano.9.199.
Testo completoAbstract (sommario):
This paper details the application of phosphorus monolayer doping of silicon on insulator substrates. There have been no previous publications dedicated to the topic of MLD on SOI, which allows for the impact of reduced substrate dimensions to be probed. The doping was done through functionalization of the substrates with chemically bound allyldiphenylphosphine dopant molecules. Following functionalization, the samples were capped and annealed to enable the diffusion of dopant atoms into the substrate and their activation. Electrical and material characterisation was carried out to determine the impact of MLD on surface quality and activation results produced by the process. MLD has proven to be highly applicable to SOI substrates producing doping levels in excess of 1 × 1019 cm−3 with minimal impact on surface quality. Hall effect data proved that reducing SOI dimensions from 66 to 13 nm lead to an increase in carrier concentration values due to the reduced volume available to the dopant for diffusion. Dopant trapping was found at both Si–SiO2 interfaces and will be problematic when attempting to reach doping levels achieved by rival techniques.
2
Wang, Xiqiao, Joseph A. Hagmann, Pradeep Namboodiri, Jonathan Wyrick, Kai Li, Roy E. Murray, Alline Myers et al. "Quantifying atom-scale dopant movement and electrical activation in Si:P monolayers". Nanoscale 10, n. 9 (2018): 4488–99. http://dx.doi.org/10.1039/c7nr07777g.
Testo completo
3
Chung, Suk, Shane R. Johnson, Ding Ding, Yong-Hang Zhang, David J. Smith e Martha R. McCartney. "Quantitative Analysis of Dopant Distribution and Activation Across p-n Junctions in AlGaAs/GaAs Light-Emitting Diodes Using Off-Axis Electron Holography". IEEE Transactions on Electron Devices 56, n. 10 (settembre 2009): 1919–23. http://dx.doi.org/10.1109/ted.2009.2025914.
Testo completoAbstract (sommario):
Off-axis electron holography has been used to measure the electrostatic potential profile across the p-n junction of an AlGaAs/GaAs light-emitting diode with linearly graded triangular AlGaAs barriers. Simulations of the junction profile showed small discrepancies with experiment when the nominal dopant concentrations of Si and Be impurities were used. Revised simulations reproduced the measurements reasonably using reduced dopant levels that reflected the efficiency of dopant activation. Band-edge diagrams simulated with the nominal and revised dopant concentrations were also compared in terms of the effect that activation efficiency had on the AlGaAs barrier shape and carrier transport. It is concluded that electron holography measurements combined with modeling offer device designers and growers a helpful tool for analyzing and confirming doping profiles in complex heterostructures.
4
Weber, W. J., C. W. Griffin e J. L. Bates. "Electrical and thermal transport properties of the Y1 − x Mx CrO3 system". Journal of Materials Research 1, n. 5 (ottobre 1986): 675–84. http://dx.doi.org/10.1557/jmr.1986.0675.
Testo completoAbstract (sommario):
The effects of substituting divalent metal ions (Mg, Ca, Sr, Ba) for Y in YCrO3 were investigated by electrical conductivity, Seebeck coefficient, and thermal conductivity measurements. The electrical conductivity results were consistent with the hopping-type conduction of a temperature-independent concentration of small polarons, with measured activation energies of 0.18-0.26 eV. The Seebeck coefficient increased nearly linearly with temperature and indicated p-type conductivity. Both electrical conductivity and Seebeck coefficient results show a strong dependence on dopant size (ionic radius) and indicate that the highest carrier concentrations were associated with Ca as the dopant, which is attributed to the similar ionic radii of Ca2+ and Y3+. The thermal conductivity decreased slightly with temperature and dopant concentration.
5
Ranchoux, B., e J. F. Currie. "Étude des corrélations entre paramètres de préparation, caractéristiques électriques et physico-chimiques d'échantillons de a-Si : H dopés ou non". Canadian Journal of Physics 63, n. 1 (1 gennaio 1985): 54–58. http://dx.doi.org/10.1139/p85-009.
Testo completoAbstract (sommario):
Using linear and second-degree regression, we have studied correlations between measurements of electrical conductivity, activation energy, concentration of the various elements (hydrogen, carbon, oxygen, argon, and eventually a dopant: indium, thalium, or antimony), thickness, and some preparation parameters: deposition temperature, mass flow ratio between the various gases intervening in the plasma, and deposition time. We have shown that the deposition rate is the only parameter, in the range studied, that plays an important role for the composition of the intrinsic films. The other parameters, viz. flow ratios of the various gases present in the mixture, temperature, have a limited influence on the composition and the electrical characteristics. The chemical composition measurements have been directly correlated with the electrical measurements. The introduction of a doping metal in the material modifies not only its opto-electrical characteristics, but generally its hydrogen content. Our process of doping by evaporation follows the "universal" behaviour of metals from columns II and V, already known in hydrogenated amorphous silicium. For the p and n films, we have observed that the hydrogen concentration and the width of the energy gap increase first with the dopant concentration and decrease afterwards. The presence of a dopant in the amorphous material leads to a disorder restructuring that changes the chemical composition more than the density of states in the energy gap.
6
Brandt, Matthias, Holger von Wenckstern, Christoph Meinecke, Tilman Butz, Holger Hochmuth, Michael Lorenz e Marius Grundmann. "Dopant activation in homoepitaxial MgZnO:P thin films". Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 27, n. 3 (2009): 1604. http://dx.doi.org/10.1116/1.3086657.
Testo completo
7
Cifuentes, N., E. R. Viana, H. Limborço, D. B. Roa, A. Abelenda, M. I. N. da Silva, M. V. B. Moreira, G. M. Ribeiro, A. G. de Oliveira e J. C. González. "Electrical Properties of Polytypic Mg Doped GaAs Nanowires". Journal of Nanomaterials 2016 (2016): 1–5. http://dx.doi.org/10.1155/2016/9451319.
Testo completoAbstract (sommario):
The electrical transport properties of individual Mg doped GaAs nanowires are investigated. It is shown that Mg can be successfully used as a nontoxic p-type dopant in GaAs nanowires. The doping levels, expanding over two orders of magnitude, and free holes mobility in the NW were obtained by the analysis of field effect transistors transfer curves. The temperature dependence of the electrical resistivity above room temperature shows that the polytypic structure of the NWs strongly modifies the NWs charge transport parameters, like the resistivity activation energy and holes mobility. At lower temperatures the NWs exhibit variable range hopping conduction. Both Mott and Efros-Shklovskii variable range hopping mechanisms were clearly identified in the nanowires.
8
Sierakowski, Kacper, Rafal Jakiela, Boleslaw Lucznik, Pawel Kwiatkowski, Malgorzata Iwinska, Marcin Turek, Hideki Sakurai, Tetsu Kachi e Michal Bockowski. "High Pressure Processing of Ion Implanted GaN". Electronics 9, n. 9 (26 agosto 2020): 1380. http://dx.doi.org/10.3390/electronics9091380.
Testo completoAbstract (sommario):
It is well known that ion implantation is one of the basic tools for semiconductor device fabrication. The implantation process itself damages, however, the crystallographic lattice of the semiconductor. Such damage can be removed by proper post-implantation annealing of the implanted material. Annealing also allows electrical activation of the dopant and creates areas of different electrical types in a semiconductor. However, such thermal treatment is particularly challenging in the case of gallium nitride since it decomposes at relatively low temperature (~800 °C) at atmospheric pressure. In order to remove the implantation damage in a GaN crystal structure, as well as activate the implanted dopants at ultra-high pressure, annealing process is proposed. It will be described in detail in this paper. P-type GaN implanted with magnesium will be briefly discussed. A possibility to analyze diffusion of any dopant in GaN will be proposed and demonstrated on the example of beryllium.
9
Song, Xi, Anne Elisabeth Bazin, Jean François Michaud, Frédéric Cayrel, Marcin Zielinski, Marc Portail, Thierry Chassagne, Emmanuel Collard e Daniel Alquier. "Electrical Characterization of Nitrogen Implanted 3C-SiC by SSRM and CTLM Measurements". Materials Science Forum 679-680 (marzo 2011): 193–96. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.193.
Testo completoAbstract (sommario):
Two electrical characterization methods were used to study 3C-SiC epilayers doped by nitrogen implantation: circular Transfer Length Method (cTLM) which allows extracting the specific contact resistance and Scanning Spreading Resistance Microscopy (SSRM) used to measure activated doping concentration. 3C-SiC samples were implanted at room temperature with different energies (ranging from 30 to 150keV) and doses (from 1 to 5.4x1015cm-2) in order to obtain a 300nm thick box-like profile at 5x1020cm-3. To activate the dopant, the samples were then annealed from 1150°C to 1350°C for 1h to 4h. Titanium-nickel c-TLM contacts annealed at 1000°C under argon showed the best results in terms of specific contact resistance (8x10-6.cm2) after a 1350°C–1h annealing. For this annealing condition, the activation rate was assessed by SSRM around 13%. This value confirms the difficulty to activate the dopants introduced into the 3C-SiC as the temperature is limited by the silicon substrate. However, this work demonstrates that low resistance values can be achieved on 3C-SiC, using nitrogen implantation at room temperature.
10
Rahim, Madatov, Najafov Arzu, Alakbarov Aydin, Tagiev Teymur e Khaliqzadeh Aydan. "Features of Electrical and Photoelectric Properties of GaS(Yb) Monocrystals". Zeitschrift für Naturforschung A 74, n. 9 (25 settembre 2019): 821–25. http://dx.doi.org/10.1515/zna-2018-0475.
Testo completoAbstract (sommario):
AbstractThe electrical and photoelectric properties of GaS(Yb) monocrystal have been studied in the range of 100–300 K. It has been established that as the partial compensation of structure defects (VGa) occurs due to the inclusion of ytterbium dopant, the electroconductivity of GaS monocrystal decreases. The simultaneously occurrence of substitution (YbGa) of cation vacancy – VYb and Yb-Ga due to the formation of acceptor and donor type two charged local centers during the doping, leads to a self-compensating process. As a result, the specific resistance of the crystal increases, and thermal activation and extinction processes are observed in the temperature dependence of photoconductivity.
Tesi sul tema "Electrical dopant activation"
1
Cornelius, Steffen. "Charge transport limits and electrical dopant activation in transparent conductive (Al,Ga):ZnO and Nb:TiO2 thin films prepared by reactive magnetron sputtering". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-156145.
Testo completoAbstract (sommario):
Transparent conductive oxides (TCOs) are key functional materials in existing and future electro-optical devices in the fields of energy efficiency, energy generation and information technology. The main application of TCOs is as thin films transparent electrodes where a combination of maximum electrical conductivity and transmittance in the visible to nearinfrared spectral range is required. However, due to the interdependence of the optical properties and the free electron density and mobility, respectively, these requirements cannot be achieved simultaneously in degenerately doped wide band-gap oxide semiconductors. Therefore, a detailed understanding of the mechanisms governing the generation of free charge carriers by extrinsic doping and the charge transport in these materials is essential for further development of high performance TCOs and corresponding deposition methods.
The present work is aimed at a comprehensive investigation of the electrical, optical and structural properties as well as the elemental composition of (Al,Ga) doped ZnO and Nb doped TiO2 thin films prepared by pulsed DC reactive magnetron sputtering. The evolution of the film properties is studied in dependence of various deposition parameters through a combination of characterization techniques including Hall-effect, spectroscopic ellipsometry, spectral photometry, X-ray diffraction, X-ray near edge absorption, Rutherford backscattering spectrometry and particle induced X-ray emission.
This approach resulted in the development of an alternative process control method based on the material specific current-voltage pressure characteristics of the reactive magnetron discharge which allows to precisely control the oxygen deficiency of the sputter deposited films.
Based on the experimental data, models have been established that describe the room temperature charge transport properties and the dielectric function of the obtained ZnO and TiO2 based transparent conductors. On the one hand, these findings allow the prediction of material specific electron mobility limits by identifying the dominating charge carrier scattering mechanisms. On the other hand, new insight is gained into the origin of the observed transition from highly conductive to electrically insulating ZnO layers upon the incorporation of increasing concentrations of Al at elevated growth temperatures.
Moreover, the Al and Ga dopant activation in ZnO have been quantified systematically for a wide range of Al concentrations and deposition conditions. A direct comparison of the Ga and Al doping efficiency demonstrates that Ga is a more efficient electron donor in ZnO. Further, it has been shown that high free electron mobilities in polycrystalline and epitaxial Nb:TiO2 layers can be achieved by reactive magnetron sputtering of TiNb alloy targets. The suppression of rutile phase formation and the control of the Nb dopant activation by fine tuning the oxygen deficiency have been identified as crucial for the growth of high quality TiO2 based TCO layers.
2
Cornelius, Steffen [Verfasser], Wolfhard [Akademischer Betreuer] Möller e Frank [Akademischer Betreuer] Richter. "Charge transport limits and electrical dopant activation in transparent conductive (Al,Ga):ZnO and Nb:TiO2 thin films prepared by reactive magnetron sputtering / Steffen Cornelius. Gutachter: Wolfhard Möller ; Frank Richter. Betreuer: Wolfhard Möller". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/106904072X/34.
Testo completo
3
Song, Xi. "Activation des dopants implantés dans le carbure de silicium (3C-SiC et 4H-SiC)". Thesis, Tours, 2012. http://www.theses.fr/2012TOUR4019/document.
Testo completoAbstract (sommario):
Ces travaux de thèse sont consacrés à l’étude de l’activation des dopants implantés dans le carbure de silicium. L’objectif est de proposer des conditions d’implantation optimisées pour réaliser le dopage de type n dans le 3C-SiC et de type p dans le 4H-SiC.Nous avons tout d’abord étudié les implantations de type n dans le 3C-SiC. Pour cela, des implantations de N, de P et une co-implantation N&P avec les recuits d’activation associés ont été étudiés. L’implantation d’azote suivie d’un recuit à 1400°C-30min a permis une activation proche de 100% tout en conservant une bonne qualité cristalline. Une étude sur les propriétés électriques des défauts étendus dans le 3C-SiC a également été réalisée. A l’aide de mesures SSRM, nous avons mis en évidence l’activité électrique de ces défauts, ce qui rend difficile la réalisation de composants électroniques sur le 3C-SiC.Nous avons ensuite réalisé une étude du dopage de type p par implantation d’Al dans le 4H-SiC, en fonction de la température d’implantation et du recuit d’activation. Nous avons pu montrer qu’une implantation à 200°C suivie d’un recuit à 1850°C-30min donne les meilleures résultats en termes de propriétés physiques et électriquesThis work was dedicated to the activation of implanted dopants in 3C-SiC and 4H-SiC. The goal is to propose optimized process conditions for n-type implantation in 3C-SiC and for p-type in 4H-SiC.We have first studied the n-type implantation in 3C-SiC. To do so, N, P implantations, N&P co-implantation and the associated annealings were performed. The nitrogen implanted sample, annealed at 1400°C-30 min evidences a dopant activation rate close to 100% while maintaining a good crystal quality. Furthermore, the electrical properties of extended defects in 3C-SiC have been studied. Using the SSRM measurements, we have evidenced for the first time that these defects have a very high electrical activity and as a consequence on future devices.Then, we have realized a study on p-type doping by Al implantation in 4H-SiC with different implantation and annealing temperatures. Al implantation at 200°C followed by an annealing at 1850°C-30min lead to the best results in terms of physical and electrical properties
4
Ruess, Frank Joachim Physics Faculty of Science UNSW. "Atomically controlled device fabrication using STM". Awarded by:University of New South Wales. Physics, 2006. http://handle.unsw.edu.au/1959.4/24855.
Testo completoAbstract (sommario):
We present the development of a novel, UHV-compatible device fabrication strategy for the realisation of nano- and atomic-scale devices in silicon by harnessing the atomic-resolution capability of a scanning tunnelling microscope (STM). We develop etched registration markers in the silicon substrate in combination with a custom-designed STM/ molecular beam epitaxy system (MBE) to solve one of the key problems in STM device fabrication ??? connecting devices, fabricated in UHV, to the outside world. Using hydrogen-based STM lithography in combination with phosphine, as a dopant source, and silicon MBE, we then go on to fabricate several planar Si:P devices on one chip, including control devices that demonstrate the efficiency of each stage of the fabrication process. We demonstrate that we can perform four terminal magnetoconductance measurements at cryogenic temperatures after ex-situ alignment of metal contacts to the buried device. Using this process, we demonstrate the lateral confinement of P dopants in a delta-doped plane to a line of width 90nm; and observe the cross-over from 2D to 1D magnetotransport. These measurements enable us to extract the wire width which is in excellent agreement with STM images of the patterned wire. We then create STM-patterned Si:P wires with widths from 90nm to 8nm that show ohmic conduction and low resistivities of 1 to 20 micro Ohm-cm respectively ??? some of the highest conductivity wires reported in silicon. We study the dominant scattering mechanisms in the wires and find that temperature-dependent magnetoconductance can be described by a combination of both 1D weak localisation and 1D electron-electron interaction theories with a potential crossover to strong localisation at lower temperatures. We present results from STM-patterned tunnel junctions with gap sizes of 50nm and 17nm exhibiting clean, non-linear characteristics. We also present preliminary conductance results from a 70nm long and 90nm wide dot between source-drain leads which show evidence of Coulomb blockade behaviour. The thesis demonstrates the viability of using STM lithography to make devices in silicon down to atomic-scale dimensions. In particular, we show the enormous potential of this technology to directly correlate images of the doped regions with ex-situ electrical device characteristics.
5
Mambou, Josiane. "Dopage au bore à partir de la phase vapeur : étude comparative des couches minces polycristallines et monocristallines de diamant". Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10055.
Testo completoAbstract (sommario):
Le diamant est un semi-conducteur tres prometteur pour les applications electroniques a haute temperature et de forte puissance. Neanmoins, pour optimiser les performances des dispositifs electroniques actuels, il est indispensable de mieux connaitre et de minimiser la concentration des defauts residuels qui limitent l'efficacite du dopage. Pour cela, nous avons elabore des couches minces de diamant dopees au bore, et etudie l'influence de l'incorporation de bore sur les proprietes du diamant et sur les defauts natifs. La caracterisation des couches s'est faite par differentes techniques : microscopie electronique a balayage (meb), absorption infrarouge (ir), diffusion raman, resonance paramagnetique electronique (rpe), diffraction x, et mesures electriques i(v,t). Les resultats obtenus montrent que les couches polycristallines et monocristallines de diamant ont un comportement similaire, ce qui indique une influence faible des joints de grains. Les mesures de diffusion raman, de diffraction x et de rpe ont montre que l'incorporation de bore dans les couches polycristallines (jusqu'a quelques 10#1#9 cm#-#3) decroit la concentration de defauts natifs. Dans cette gamme de dopage, la qualite des films homoepitaxies est meilleure que celle du substrat. Les mesures d'absorption infrarouge a 300k ont permis de calculer la concentration en bore dans la phase solide, et de mettre en evidence l'inhomogeneite de l'incorporation de bore dans les couches polycristallines. Les faibles concentrations de defauts de type n compensateurs (< quelques 10#1#5 cm#-#3) ont ete deduites des mesures de resistivites et de leurs energies d'activation a haute temperature. Ce dernier resultat est tres prometteur pour les applications electroniques.
6
Chen, Hsin-Cheng, e 陳信誠. "Study on the influences of co-doping and initial layers on dopant activation and opto-electrical properties". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/92360621859382094080.
Testo completoAbstract (sommario):
碩士南台科技大學
機械工程系
98
The purpose of this study is to investigate the influences of doping Al (Al/Zn=0.~5 at.%) and co-doping Al and Mg (Al/Zn=0.25~1.0 at.%、Mg/Zn=0.0 ~1.0 at.%) by using sol-gel method at the different growth behaviors (Rapid Thermal Annealing,tube furnace and radio frequency sputtering system) on the precursor compounds, micro-structural, surface morphology and optoelectronic properties of ZnO thin films and to find the best proportion of doping so that high quality of transparent conductive films can be obtained. In this experiment, the precursor was prepared by sol-gel method. We used two processes. First, Zinc acetate dehydrate was added into alcohol solvent. Then, MEA was added as stabilizer. Afterwards, adequate amount of metallic ions . Next, spin-coating was carried out on a glass substrate (corning eagle 2000). After different heat-treatments, the films were obtained. Second, process using RF sputtering with sol-gel method, rapid thermal annealing in the way of the films grain growth will not be subject to the direction of the initial layers.We used the sputtering process to create an initial layer on the glass substrate of the thicknesses of the initial layers were tens to hundreds of nanometers have also promoted the growth of the ZnO crystallites in the (002) direction. The specimens were optoelectronic properties analyzed by UV-Vis-NIR, SE, Hall and Four-Point Probe, and TF-XRD, FE-SEM patterns demonstrated that the preferential orientation of the films, XPS which are mainly used to analyze the influences on the dopant activation, and FTIR of activation compounds in Mg-doped ZnO films. Experimental results show that the lowest resistance of 2.66×10-3Ωcm was obtained with 0.75 at.% Al and 0.5 at.% Mg. The transmittance of the ZnO:(Al, Mg) films was over 80%. Because RTA process that the growth of the films began inside the sol-layer. However, TF process that the of the films began inside the substrate heated to different films growth characteristics than the favorable effect of dopant activation. Second, RF sputtering with sol-gel method of the resistivity was not improved. The application of a high quality initial layer could enhance the crystallographic quality of the ZnO films.
7
Wang, Yu-Long, e 王裕隆. "Improving electrical characteristics of Fin-shaped Tunneling-Field-Effect-Transistor using Microwave dopant activation and Asymmetry structure". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/45990305348300769134.
Testo completoAbstract (sommario):
碩士國立清華大學
工程與系統科學系
101
The market demand for portable electric equipment increase dramatically year by year. Although transistors develop toward low cost and high density, maintaining device characteristics becomes difficult due to the device fabrication and physics limitations of the device. Designing a device that different from conventional MOSFET is a necessary way. This thesis based on Fin-shaped Tunneling Transistor which operated by quantum tunneling mechanism. Thus, compared with conventional MOSFET operated by drift mechanism, the Tunneling Transistor can achieve fast on/off characteristic. By the Fin-shaped structure, it can affect the active layer electric potential distribution by multi-direction, increasing the gate control ability and enhance the characteristics. Above the discussion, the Fin-shaped tunneling transistor is a device with high-efficiency and good transfer characteristic. In this thesis, we focus on demonstrate that microwave dopant activation technique can help TFETs to form an abrupt tunneling junction. Subthreshold slope and driving current can be greatly enhanced by microwave annealing as the dopant activation method compare to traditional rapid thermal annealing. An interesting phenomenon of negative differential conductance in the output characteristic was observed, which is attributed to hot-carrier effect at the high gate overdrive operation. A positive temperature dependence of transfer characteristic is also observed, which is related to the bandgap narrowing effect and the enhancement of the thermionic field emissions of the grain boundary states. Finally, with the geometric difference between source and drain, we demonstrate a device with high on-state current and low off-state current, simultaneously. This work shows experimental data for device’s reliability; all the data can display Fin-shaped tunneling transistor has applied to high value actually, it would become the next-generation device.
8
Cornelius, Steffen. "Charge transport limits and electrical dopant activation in transparent conductive (Al,Ga):ZnO and Nb:TiO2 thin films prepared by reactive magnetron sputtering: Charge transport limits and electrical dopant activation in transparent conductive (Al,Ga):ZnO and Nb:TiO2 thin films prepared by reactive magnetron sputtering". Doctoral thesis, 2013. https://tud.qucosa.de/id/qucosa%3A28409.
Testo completoAbstract (sommario):
Transparent conductive oxides (TCOs) are key functional materials in existing and future electro-optical devices in the fields of energy efficiency, energy generation and information technology. The main application of TCOs is as thin films transparent electrodes where a combination of maximum electrical conductivity and transmittance in the visible to nearinfrared spectral range is required. However, due to the interdependence of the optical properties and the free electron density and mobility, respectively, these requirements cannot be achieved simultaneously in degenerately doped wide band-gap oxide semiconductors. Therefore, a detailed understanding of the mechanisms governing the generation of free charge carriers by extrinsic doping and the charge transport in these materials is essential for further development of high performance TCOs and corresponding deposition methods.
The present work is aimed at a comprehensive investigation of the electrical, optical and structural properties as well as the elemental composition of (Al,Ga) doped ZnO and Nb doped TiO2 thin films prepared by pulsed DC reactive magnetron sputtering. The evolution of the film properties is studied in dependence of various deposition parameters through a combination of characterization techniques including Hall-effect, spectroscopic ellipsometry, spectral photometry, X-ray diffraction, X-ray near edge absorption, Rutherford backscattering spectrometry and particle induced X-ray emission.
This approach resulted in the development of an alternative process control method based on the material specific current-voltage pressure characteristics of the reactive magnetron discharge which allows to precisely control the oxygen deficiency of the sputter deposited films.
Based on the experimental data, models have been established that describe the room temperature charge transport properties and the dielectric function of the obtained ZnO and TiO2 based transparent conductors. On the one hand, these findings allow the prediction of material specific electron mobility limits by identifying the dominating charge carrier scattering mechanisms. On the other hand, new insight is gained into the origin of the observed transition from highly conductive to electrically insulating ZnO layers upon the incorporation of increasing concentrations of Al at elevated growth temperatures.
Moreover, the Al and Ga dopant activation in ZnO have been quantified systematically for a wide range of Al concentrations and deposition conditions. A direct comparison of the Ga and Al doping efficiency demonstrates that Ga is a more efficient electron donor in ZnO. Further, it has been shown that high free electron mobilities in polycrystalline and epitaxial Nb:TiO2 layers can be achieved by reactive magnetron sputtering of TiNb alloy targets. The suppression of rutile phase formation and the control of the Nb dopant activation by fine tuning the oxygen deficiency have been identified as crucial for the growth of high quality TiO2 based TCO layers.
9
Mtangi, Wilbert. "Electrical characterization of process, annealing and irradiation induced defects in ZnO". Thesis, 2012. http://hdl.handle.net/2263/30356.
Testo completoAbstract (sommario):
A study of defects in semiconductors is vital as defects tend to influence device operation by modifying their electrical and optoelectronic properties. This influence can at times be desirable in the case of fast switching devices and sometimes undesirable as they may reduce the efficiency of optoelectronic devices. ZnO is a wide bandgap material with a potential for fabricating UV light emitting diodes, lasers and white lighting devices only after the realization of reproducible p-type material. The realization of p-type material is greatly affected by doping asymmetry. The self-compensation behaviour by its native defects has hindered the success in obtaining the p-type material. Hence there is need to understand the electronic properties, formation and annealing-out of these defects for controlled material doping. Space charge spectroscopic techniques are powerful tools for studying the electronic properties of electrically active defects in semiconductors since they can reveal information about the defect “signatures”. In this study, novel Schottky contacts with low leakage currents of the order of 10-11 A at 2.0 V, barrier heights of 0.60 – 0.80 eV and low series resistance, fabricated on hydrogen peroxide treated melt-grown single crystal ZnO samples, were demonstrated. Investigations on the dependence of the Schottky contact parameters on fabrication techniques and different metals were performed. Resistive evaporation proved to produce contacts with lower series resistance, higher barrier heights and low reverse currents compared to the electron-beam deposition technique. Deep level transient spectroscopy (DLTS) and Laplace-DLTS have been employed to study the electronic properties of electrically active deep level defects in ZnO. Results revealed the presence of three prominent deep level defects (E1, E2 and E3) in the as-received ZnO samples. Electron-beam deposited contacts indicated the presence of the E1, E2 and E3 and the introduction of new deep level defects. These induced deep levels have been attributed to stray electrons and ionized particles, present in the deposition system during contact fabrication. Exposure of ZnO to high temperatures induces deep level defects. Annealing samples in the 300°C – 600°C temperature range in Ar + O2 induces the E4 deep level with a very high capture cross-section. This deep level transforms at every annealing temperature. Its instability at room temperature has been demonstrated by a change in the peak temperature position with time. This deep level was broad, indicating that it consists of two or more closely spaced energy levels. Laplace-DLTS was successfully employed to resolve the closely spaced energy levels. Annealing samples at 700°C in Ar and O2 anneals-out E4 and induces the Ex deep level defect with an activation enthalpy of approximately 160 – 180 meV. Vacuum annealing performed in the 400°C – 700°C temperature range did not induce any deep level defects. Since the radiation hardness of ZnO is crucial in space applications, 1.6 MeV proton irradiation was performed. DLTS revealed the introduction of the E4 deep level with an activation enthalpy of approximately 530 meV, which proved to be stable at room temperature and atmospheric pressure since its properties didn’t change over a period of 12 months.Thesis (PhD)--University of Pretoria, 2013.
Physics
unrestricted
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Zong, Shuang. "Preparation of N-doped porous carbon materials and their supercapacitator performance". Diss., 2021. http://hdl.handle.net/10500/27435.
Testo completoAbstract (sommario):
Supercapacitor is the best potential candidate of the energy storage system due to the
superior charge or discharge efficiency, high power density (>10 kW kg-1), and long cycling life. Porous carbon materials as the promising electrode material have been widely used in supercapacitor. In fact, conventional porous carbon supercapacitor electrodes cannot fulfil the growing demand of high energy and power densities of supercapacitor. A large number of studies show that nitrogen doping can change the surface electronic structure of carbon materials, thus significantly improving the electrochemical properties. In addition to, the pore structure and morphology of carbon materials have great influence on the electrochemical performance. In this work, we firstly fabricated nitrogen-doped porous carbon nanotubes by using a simple mixed salts (NaCl/ZnCl2) activation strategy. The as-obtained porous carbon nanotubes exhibited excellent electrochemical performance in supercapacitor. Furthermore, two- dimension nitrogen-doping porous nanosheets were prepared by a salt template-assisted monomer deposition method. In this study, by optimizing the synthesis conditions, the as-obtained carbon nanosheets showed a high specific capacitance of 277 F g-1 at 1 A g-1 and excellent cycle stability retained 91 % after 10,000 cycles.College of Engineering, Science and Technology
M. Tech.( Civil and Chemical Engineering
Capitoli di libri sul tema "Electrical dopant activation"
1
Johnson, C. M., P. Kringhøj e M. C. Ridgway. "The influence of non-stoichiometry on dopant electrical activation and depth distribution in InP implanted with Group IV or VI elements". In Ion Beam Modification of Materials, 895–98. Elsevier, 1996. http://dx.doi.org/10.1016/b978-0-444-82334-2.50176-3.
Testo completo
2
Sridhar, Rapolu, D. Ravinder, J. Laxman Naik, K. Vijaya Kumar, N. Maramu e S. Katlakunta. "Investigation of Structural, Magnetic and Electrical Properties of Chromium Substituted Nickel Ceramic Nanopowders". In Advanced Ceramic Materials. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94941.
Testo completoAbstract (sommario):
Nano-ceramic of NiCrxFe2-xO4 (0.1 ≤ x ≤ 1.0) ferrites were synthesized by citrate-gel auto combustion method. The structural parameter such as lattice parameter, X-ray density, bulk density and porosity variations with Cr doping were studied. The average crystallite size is in the range 8.5–10.5 nm. The surface morphology and elemental analysis was studied with SEM (EDAX) spectrum and the structural information analyzed with FTIR spectra. Magnetic properties were discussed with Cr3+ion concentration. Electrical parameters like dc resistivity and drift mobility were reported with function of temperature and dopent concentration from room temperature to well beyond Curie temperature and explained with hopping mechanism between Fe2+↔Fe3+ ions. The activation energies in ferri and para magnetic regions were investigated. Dielectric parameters like dielectric constant, dielectric loss and ac conductivity were investigated variation with frequency and composition.
Atti di convegni sul tema "Electrical dopant activation"
1
Ivanov, Denis, Ilya Marinov, Yuriy Gorbachev, Alexander Smirnov e Valeria Krzhizhanovskaya. "Computer Simulation of Laser Annealing of a Nanostructured Surface". In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87087.
Testo completoAbstract (sommario):
Laser annealing technology is used in mass production of new-generation semiconductor materials and nano-electronic devices like the MOS-based (metal–oxide–semiconductor) integrated circuits. Manufacturing sub-100 nm MOS devices demands application of ultra-shallow doping (junctions), which requires rapid high-temperature annealing to increase dopant electrical activation and remove implantation defects in the silicon [1].