Dissertations / Theses on the topic 'Nanojunction'
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Wu, Qingqing. "Theory of molecular-scale transport in graphene nanojunctions." Thesis, Lancaster University, 2018. http://eprints.lancs.ac.uk/126477/.
Full textSoria, Martínez Rubén. "Modeling of local excitation processes in molecular nanojunctions." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE017.
Full textOne of the most remarkable applications of the tunnel effect is the Scanning Tunneling Microscope (STM), allowing to get the spatially and energetically map distribution of electrons on the surface of materials with nanometric resolution. Recent advances make it possible to exploit the tip of the STM as a source of local excitation of materials. The work presented in this manuscript aims to describe and model the phenomena involved in such excitation process. We present a modeling of the absorption spectra of phthalocyanine molecules lying on surfaces within the framework of the time-dependent density functional theory (TD-DFT). We show that spectroscopic analysis of the transitions between the ground state and the excited states of the molecule allows to characterize the stress inside the molecule. We also highlight a variety of excitation spectra depending on the location of the excitation of the molecule. We discuss the possibility of exploiting this phenomenon to characterize inter-molecular energy transport
Ghader, Doried. "Theory for ballistic magnon transport across disordered magnetic nanojunctions." Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1020.
Full textThe aim of this thesis is to develop theoretical and numerical methods to analyze the ballistic spin waves scattering and transport across two types of rare earth - transition metals disordered magnetic nanomaterials, namely the cobalt-gadolinium and the iron-gadolinium types, as building blocks for nanojunction systems. The theoretical computations developed in this work account properly for the consequences of the characteristic disorder present in these systems, whether alloy disorder for the former or structural amorphous-like disorder for the latter. The developed methods serve, in particular, to explore the attributes of these nanojunctions as filters and elements for resonance assisted transmission in a magnonic device. The thesis develops a novel and dynamic non-local version of the coherent potential approximation (DNLCPA), to study the spin dynamics on disordered ultrathin Co-Gd and Fe-Gd magnetic systems. The dynamic random scattering potentials are derived in a completely novel approach, exploiting the phase properties of the elementary spin excitations within the Dyson formalism. This approach is then developed in two different fundamental manners, and applied appropriately for the disordered nanosystems presenting alloy and structural disorder. The DNLCPA approach is incorporated with the phase field matching theory (PFMT) to study the spin waves ballistic transport across the Co-Gd and the Fe-Gd nanojunctions, sandwiched between Co and Fe leads respectively. This PFMT-DNLCPA method yields for the first time the description of the scattering and transport properties for the spin waves incident on the nanojunctions. Furthermore, our computations successfully demonstrate, model and quantify the diffusive energy loss in ballistic scattering due to each type of disorder
Niklas, Michael [Verfasser], Milena [Akademischer Betreuer] Grifoni, and Sigmund [Akademischer Betreuer] Kohler. "Current and noise properties of interacting nanojunctions / Michael Niklas ; Milena Grifoni, Sigmund Kohler." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1162339713/34.
Full textHardrat, Björn [Verfasser]. "Ballistic transport in one-dimensional magnetic nanojunctions: A first-principles Wannier function approach / Björn Hardrat." Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1028798954/34.
Full textGerster, Daniel Friedrich [Verfasser], Johannes V. [Akademischer Betreuer] Barth, and Alexander W. [Akademischer Betreuer] Holleitner. "Light-induced electron motion in nanojunctions / Daniel Friedrich Gerster. Gutachter: Johannes V. Barth ; Alexander W. Holleitner. Betreuer: Johannes V. Barth." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1024161498/34.
Full textYao, Hsuan-Te, and 姚宣德. "Thermoelectric effect in nanojunction." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/71837947895620887562.
Full text國立交通大學
電子物理系所
100
Using first-principles approaches, we have investigated the thermoelectric properties of two different systems of nano-junction. The first system is Carbon-atoms chains connecting bimetal junction, and the other one is paired metal-Br-Al junction. In Carbon-atoms chains system, we observe odd-even effects in the Seebeck coefficient of carbon-atom chains as the number of carbon atoms increases. The Seebeck coefficients show minus signs for the odd-numbered atomic chains and plus signs for the even-numbered atomic chains in low temperatures regime. The reason for the odd-even effects is that the tangent of transmission functions near the chemical potential (Fermi level) change signs as the number of carbon atoms in the junction increases. In the paired metal-Br-Al junction, we have investigated the thermoelectric properties and energy conversion efficiency. Owing to the narrow states in the vicinity of the chemical potential, the nanojunction has large Seebeck coefficients such that it can be considered an efficient thermoelectric power generator.We also consider the nanojunction in a three-terminal geometry, where the current, voltage, power, and efficiency can be efficiently modulated by the gate voltages. Such current_voltage characteristics could be useful in the design of nanoscale electronic devices such as a transistor or switch.
Fu, Hui-Chun, and 傅惠君. "Ultrahigh sensitivity ZnO nanosensor with Schottky nanojunction." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/24571800648428713760.
Full text淡江大學
物理學系碩士班
100
One-dimensional nanostructures have been demonstrated as outstanding materials for fabricating ultrasensitive nanosensors .In order to obtain gigantic sensitivity, our research team had proposed such a new mechanism, schottky-gate effect, Schottky-contacted device can enhance the sensitivity of nanosensor devices dramatically. In this study, we deliberately introduce a point contact of nonsymmetrical Schottky junction (PCSJ). The sensitivity of this new device can be greatly enhanced due to the nano Schottky contact area. The signal sensitivity was more than 2500%, the response and reset time of UV sensing are less than 1s. This work will provide a new technology to design the nanodevice and nanosensor.
Chen, Hong-Yang, and 陳紘揚. "Hybrid ZnO nanorods array /polymer nanojunction photovoltaic solar cells." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/09225367627595142173.
Full text國立交通大學
材料科學與工程系所
95
This research focus on the preparation of hybrid polymer/zinc oxide (ZnO) solar cells, in which the ZnO rods grown perpendicularly on ITO substrates, as a means to provide a direct and ordered path for photogenerated electrons to the collecting electrode. We use sol-gel method to fabricate ZnO backing layer and low-temperature solution-based growth techniques to grow ZnO nanostructures. Different backing layer thickness, heat-treatment condition, growth time were investigated for solar cell application .After deposit polymer, using scanning electron microscopy, absorption spectroscopy and photovoltaic device measurements to study the morphology and device performance of the prepared structures. The dependence of the photovoltaic performance on the ZnO nanorods length and the organic layer thickness was investigated. Under AM1.5(100mWcm -2) global solar condition, the best ZnO nanorods/ poly(3-hexylthiophene) photovoltaic device yields power conversion efficiency 0.909% and a peak external quantum efficiency 22% at 460nm. The power conversion efficiency of it is tree times as large as that of ZnO film/ regioregular poly(3-hexylthiophene) bilayer system. The ZnO / polythiophene device is limited in photocurrent due to the large spacing between the ZnO fibers. This is overcome by blending PCBM into the polythiophene film and can enhance power conversion efficiency to 1.01%.
Yi-YingChen and 陳怡穎. "Preconcentration, Separation, and Guidance of Mixed-Species Samples Near a Nanojunction in Micro–Nanofluidic Device." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/h33mpu.
Full textSquillantini, Lorenzo. "Spin Crossover complexes: from synthesis to surface assembly." Doctoral thesis, 2021. http://hdl.handle.net/2158/1235501.
Full text"Electrical and Optical Characterization of Molecular Nanojunctions." Thesis, 2011. http://hdl.handle.net/1911/70488.
Full textEvans, Kenneth. "Nanocrystal-based optoelectronic devices in plamonic nanojunctions." Thesis, 2012. http://hdl.handle.net/1911/71295.
Full textChen, Yu-Chang, and 陳昱璋. "Wannier functions of magnetic atoms in nanojunctions and bulk materials." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/hms6r2.
Full text國立交通大學
電子物理系所
102
In this thesis, we have applied the maximally localized Wannier function approach[Wannier90] to a density function theory based first principle code[Quantum espresso]. In order to understand the behavior of magnetic atom in different environment, we calculate three different systems which are isolated atom system, CuCoCu nanojunction system and Co doped in Cu bulk system. We found that magnetic properties, PDOS and Maximally localized Wannier functions will be varied depends on the symmetry between the magnetic d orbital and nearest atoms around it. We also found spreads of MLWF will be changed depending on distance between MLWF and nearest atoms around it and spreads also depends on spin if it is a spin polarized case.
Rajasekaran, Rajesh. "Preparation and characterization of materials for tunneling and ballistic nanojunctions." 2008. http://proquest.umi.com/pqdweb?did=1650505441&sid=9&Fmt=2&clientId=14215&RQT=309&VName=PQD.
Full textTitle from title screen (site viewed Apr. 9, 2009). PDF text: v, 156 p. : ill. (some col.) ; 9 Mb. UMI publication number: AAT 3338831. Includes bibliographical references. Also available in microfilm and microfiche formats.
Liang, Yen-Tzu, and 梁晏慈. "The Effect of Photon-induced Hot-electron on Tunneling Efficiency across Nanojunctions." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/48854961735722458325.
Full text國立臺灣大學
化學研究所
104
The fundamental of molecular electronics involves electron-transport through electrode-molecule-electrode junctions. The transporting efficiency can be correlated to barrier height by tunneling decay constant. The interaction of molecular electronics with plasmons, collective oscillations of free electrons coupling to electromagnetic fields, has drawn lots of attentions. The formation of hot electrons from surface plasmon decay results in photocurrent. In addition, hot electron can also be generated from photoexcitation. We measure the tunneling phenomenon without molecules bridging between electrodes and the responses of gold and silver electrodes, solvent including octylbenzene and propylene carbonate, and electromagnetic field to tunneling decay constant by scanning tunneling microscopy break junction (STM BJ). The tunneling decay constant is reduced for silver electrodes in propylene carbonate when irradiated, that would be realized by comparing the work function of metal, polarity of solvent and by the presence of hot electrons. Following the concept of hot electrons, we investigate the increased conductance of molecules that binding to Au electrodes via head group under illumination and explain the differences in the conductance enhancement of 2,7-diaminofluorene and 4,4′-bipyridine.