Dissertations / Theses on the topic 'Devices'
To see the other types of publications on this topic, follow the link: Devices.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Devices.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hui, Kwun-nam. "Device optimization studies of organic light emitting devices." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36578484.
Full text
2
Hui, Kwun-nam, and 許冠南. "Device optimization studies of organic light emitting devices." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36578484.
Full text
3
Macabebe, Erees Queen Barrido. "Investigation of device and performance parameters of photovoltaic devices." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1003.
Full textAbstract:
In order to investigate the influence of parasitic resistances, saturation current and diode ideality factor on the performance of photovoltaic devices, parameter extraction routines employing the standard iteration (SI) method and the particle swarm optimization (PSO) method were developed to extract the series resistance, shunt resistance, saturation current and ideality factor from the I-V characteristics of solar cells and PV modules. The well-known one- and two-diode models were used to describe the behavior of the I-V curve and the parameters of the models were determined by approximation and iteration techniques. The SI and the PSO extraction programmes were used to assess the suitability of the one- and the two-diode solar cell models in describing the I-V characteristics of mono- and multicrystalline silicon solar cells, CISS- and CIGSS-based solar cells. This exercise revealed that the two-diode model provides more information regarding the different processes involved in solar cell operation. Between the two methods developed, the PSO method is faster, yielded fitted curves with lower standard deviation of residuals and, therefore, was the preferred extraction method. The PSO method was then used to extract the device parameters of CISS-based solar cells with the CISS layer selenized under different selenization process conditions and CIGSS-based solar cells with varying i-ZnO layer thickness. For the CISS-based solar cells, the detrimental effect of parasitic resistances on device performance increased when the temperature and duration of the selenization process was increased. For the CIGSS-based devices, photogeneration improved with increasing i-ZnO layer thickness. At high forward bias, bulk recombination and/or tunneling-assisted recombination were the dominant processes affecting the I-V characteristics of the devices. v Lastly, device and performance parameters of mono-, multicrystalline silicon and CIS modules derived from I-V characteristics obtained under dark and illuminated conditions were analyzed considering the effects of temperature on the performance of the devices. Results showed that the effects of parasitic resistances are greater under illumination and, under outdoor conditions, the values further declined due to increasing temperature. The saturation current and ideality factor also increased under outdoor conditions which suggest increased recombination and, coupled with the adverse effects of parasitic resistances, these factors result in lower FF and lower maximum power point. Analysis performed on crystalline silicon and thin film devices utilized in this study revealed that parameter extraction from I-V characteristics of photovoltaic devices and, in particular, the implementation of PSO in solar cell device parameter extraction developed in this work is a useful characterization technique.
4
Solis, Adrian (Adrian Orbita). "MIT Device Simulation WebLab : an online simulator for microelectronic devices." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33364.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, June 2005.Includes bibliographical references (p. 149-157).
In the field of microelectronics, a device simulator is an important engineering tool with tremendous educational value. With a device simulator, a student can examine the characteristics of a microelectronic device described by a particular model. This makes it easier to develop an intuition for the general behavior of that device and examine the impact of particular device parameters on device characteristics. In this thesis, we designed and implemented the MIT Device Simulation WebLab ("WeblabSim"), an online simulator for exploring the behavior of microelectronic devices. WeblabSim makes a device simulator readily available to users on the web anywhere, and at any time. Through a Java applet interface, a user connected to the Internet specifies and submits a simulation to the system. A program performs the simulation on a computer that can be located anywhere else on the Internet. The results are then sent back to the user's applet for graphing and further analysis. The WeblabSim system uses a three-tier design based on the iLab Batched Experiment Architecture. It consists of a client applet that lets users configure simulations, a laboratory server that runs them, and a generic service broker that mediates between the two through SOAP-based web services. We have implemented a graphical client applet, based on the client used by the MIT Microelectronics WebLab.
(cont.) Our laboratory server has a distributed, modular design consisting of a data store, several worker servers that run simulations, and a master server that acts as a coordinator. On this system, we have successfully deployed WinSpice, a circuit simulator based on Berkeley Spice3F4. Our initial experiences with WeblabSim indicate that it is feature-complete, reliable and efficient. We are satisfied that it is ready for beta deployment in a classroom setting, which we hope to do in Fall 2004.
by Adrian Solis.
M.Eng.
5
Lee, Gregory S. "Low power haptic devices : ramifications on perception and device design /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5863.
Full text
6
Da, Ponte Ana Sofia Lopes. "Daydreaming Devices." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45960.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2008.Includes bibliographical references (leaves 62-65).
Daydreaming Devices is a project on aspects of daydream and the design of convertible furniture within the context of art. This thesis addresses the concepts and the design of two daydreaming devices developed during my studies at MIT, the Dreaming Lounge and the Working Unit. Both works create a place for contemplation and generate what I call "ambiguous forms of knowledge." These art works cultivate relations between personal and collective agency while demystifying implicit aspects of socialization. They were designed as utilitarian and emotional artifacts; existing in public or semipublic spaces, they reach their maximum potential when activated within a group of people. Their aim is to affect an understanding of the waking life, sometimes uselessly and strictly relegated to the obscurity of intimacy.
by Ana Sofia Lopes da Ponte.
S.M.
7
Kwong, Chung-yin Calvin. "Improving the performance of organic optoelectronic devices by optimizing device structures." Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B31452693.
Full text
8
Bolognesi, Margherita. "Organic bulk-heterojunction photovoltaic devices: materials, device architectures and interfacial processes." Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/128202.
Full textAbstract:
Research on organic photovoltaic devices (OPV) has developed during the past 30 years, but especially in the last decade it has attracted scientific and economic interest triggered by a rapid increase in power conversion efficiencies. Thanks to the indtroduction of the bulk heterojunction (BHJ) concept, today BHJ OPV efficiencies are exceeding 9%. This thesis gives an overview on the different possible strategies that could be adopted for a further. improvement of BHJ OPV devices performances. The accurate analysis of the chemical, energetic and physical criteria governing the solar cells functioning allowed to individuate some critical aspects and apply possible solutions by a fine tuning of the materials chemical structures, device processing techniques and device architecture engineering. Even though noit in all cases the applied strategy successfully led to device efficiency improvements, the fundamental understanding of some of the efficiency limiting factors could serve as useful scientific basis for future developments.
9
Kwong, Chung-yin Calvin, and 鄺頌賢. "Improving the performance of organic optoelectronic devices by optimizing device structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31452693.
Full text
10
VASSY, LOUIS PETERSON. "OPTIMIZATION OF DEVICE PERFORMANCE IN 1x2 SYMMETRIC INTERFERENCE MULTIMODE INTERFERENCE DEVICES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1053359061.
Full text
11
Vassy, Louis P. "Optimization of device performance in 1x2 symmetric interference mulitmode interference devices." Cincinnati, Ohio : University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1053359061.
Full text
12
Rakheja, Shaloo. "Interconnects for post-CMOS devices: physical limits and device and circuit implications." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45866.
Full textAbstract:
The objective of this dissertation is to classify the opportunities, advantages, and limits of novel interconnects for post-CMOS logic that can augment or eventually replace the CMOS logic. Post-CMOS devices are envisaged on the idea of using state variables other than the electron charge to store and manipulate information. In the first component of the thesis, a comprehensive analysis of the performance and the energy dissipation of novel logic based on various state variables is conducted, and it is demonstrated that the interconnects will continue to be a major challenge even for post-CMOS logic.
The second component of the thesis is focused on the analysis of the interconnection aspects of spin-based logic. This research goal is accomplished through the development of physically-based models of spin-transport parameters for various metallic, semiconducting, and graphene nanoribbon interconnects by incorporating the impact of size effects for narrow cross-sectional dimensions of all-spin logic devices. Due to the generic nature of the models, they can be used in the analysis of spin-based devices to study their functionality and performance more accurately. The compact nature of the models allows them to be easily embedded into the developing CAD tools for spintronic logic. These models then provide the foundation for (i) analyzing the spin injection and transport efficiency in an all-spin logic circuit with various interconnect materials, and (ii) estimating the repeater-insertion requirements in all-spin logic, and (iii) estimating the maximum circuit size for all-spin logic. The research is crucial in pinpointing the implications of the physical limits of novel interconnects at the material, device, circuit, and architecture levels.
13
Agnihotri, Vikrant 1981. "Towards in-situ device fabrication : electrostatic lithography and nanowire field effect devices." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30264.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (leaves 79-80).
Electron beams were used to deposit fine line-width charge in electret materials. The electrets were exposed to charged or polarizable nanoparticle precursors. These nanoparticles decorate the charge pattern. Electret materials including Mylar, Polyamide and Teflon were used for this process. Nanoparticles used ranged from carbon black, gold, silver, iron oxide, aluminum oxide and silicon oxide. Multiple nanoparticle delivery methods were employed including immersion in a nanoparticle solution, exposure to a nanoparticle aerosol, electrosprayed nanoparticles and in-situ delivery of nanoparticles. The technique was adapted to produce the fastest known electron beam resist with exposure dosage as low as 10 nC/cm2. We have termed the new resist an electrostatic resist and the technique electrostatic lithography. A novel technique to fabricate logic elements from semiconducting nanowires grown using vapor-liquid-solid mechanism was also developed. The technique involves source, drain, gate-oxide and gate material fabrication using electron beam induced chemical vapor deposition. Field effect transistor and ring oscillator architectures were fabricated using this process. Nanowires were characterized using scanning electron microscopy and transmission electron microscopy. Current-voltage measurements were performed on the nanowire field effect transistors.
by Vikrant Agnihotri.
S.M.
14
Shea, Patrick. "DESIGN AND MODELING OF RADIATION HARDENED LDMOSFET FOR SPACE CRAFT POWER SYSTEMS." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2822.
Full textAbstract:
NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device's parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects.M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE
15
Ellch, Jonathan P. "Fingerprinting 802.11 devices." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FEllch.pdf.
Full textAbstract:
Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2006.Thesis Advisor(s): Dennis Volpano and Chris Eagle. "September 2006." Includes bibliographical references (p. 67). Also available in print.
16
Myrén, Niklas. "Poled fiber devices." Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262.
Full textAbstract:
The topic of this thesis is the development of devices for telecom applications based on poled optical fibers. The focus is on a specific function, optical switching/modulation.
Some of the most important results are summarized below. Optical switching at telecom wavelengths (1.55 μm) is demonstrated in an all-fiber switch based on a fiber with internal electrodes. The fiber is made electro-optically active with a thermal poling process in which a strong electric field is recorded in the glass at a temperature of 255 °C. After poling, the fiber is put in one arm of a Mach-Zehnder interferometer and by applying a voltage across the two electrodes the refractive index is modulated and the optical signal switched from one output port to the other. A switching voltage of 190 V at 1550 nm was achieved, which to the best of our knowledge is the lowest value reported. By carefully matching the lengths of the fibers in the two arms of the interferometer the optical bandwidth could be made as large as 20 nm. The extinction ratio, determined by the power ratio in the two arms, was 30 dB and the highest modulation frequency was 30 MHz. Poled fibers were packaged to increase the thermal and mechanical stability and to make handling easier. 40 Gb/s transmission test through the device showed no bit-error-rate performance degradation. Protection switching of a 10 Gb/s signal is also demonstrated.
The depletion region in a poled fiber was found to be wedge-shaped and very wide, 13 μm and completely overlapped with the core. In a time-resolved poling experiment the recorded electric field was measured. The sign of the field changed after ~20 min, when the depletion region passed through the core, which led to the conclusion that an electric field is present also outside of the depletion region.
A ring laser was constructed with an erbium doped fiber as the gain medium. A fiber modulator was placed inside the cavity and when a small RF signal, with a frequency matched to the cavity ground frequency, was applied to the modulator the laser was modelocked. The output pulse train contained pulses of sub ns duration and is the first demonstration of mode-locking using poled fibers.
A sampled grating with 16 channels spaced by 50 GHz was inserted into the cavity. The fiber modulator had optical bandwidth of 7 nm with center wavelength that depends on the applied voltage. By applying of 10 – 210 V to the modulator it was possible to tune the laser to 11 of the 16 channels for a total tuning range of over 4 nm.
A scheme to deposit 1 μm thin silver electrodes inside the holes of an optical fiber is demonstrated together with a new method of creating periodic electrodes by periodically ablating the silver film electrodes. The periodic electrodes are used to create a quasi-phase matched (QPM) nonlinearity in a fibers which is showed in a proof of principle experiment.
17
Seidel, Robert Viktor. "Carbon Nanotube Devices." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1107768324667-82312.
Full textAbstract:
Eine Reihe wichtiger Wachstums- und Integrationsaspekte von Kohlenstoff-Nanoröhren wurde im Rahmen dieser Arbeit untersucht. Der Schwerpunkt der experimentellen Arbeit lag dabei hauptsächlich bei einschaligen Kohlenstoffnanoröhren (SWCNT). Das große Potential dieser Nanoröhren für Transistor-Anwendungen wurde durch die Herstellung einer Vielzahl funktionierender Bauelemente aus diesen Kohlenstoffnanoröhren mittels relativ einfacher Herstellungsprozesse demonstriert. Ein fundiertes Verständnis für die Abhängigkeiten des Nanoröhrenwachstums von einer Vielzahl an Parametern wurde mit Hilfe mehrerer tausend Wachstumsexperimente gesammelt. Verschiedene Katalysatormetalle, Kohlenstoffquellen und Katalysatorunterlagen wurden detailliert untersucht. Ein Hauptaugenmerk wurde dabei auf eine Reduzierung der Wachstumstemperatur gerichtet. Die niedrige Wachstumstemperatur spielt eine große Rolle für eine möglichst hohe Kompatibilität mit konventionellen Herstellungsverfahren der Silizium-Halbleitertechnik. Ein einfaches phänomenologisches Wachstumsmodell wurde für die Synthese von Nanoröhren mittels katalytisch-chemischer Gasphasen-Abscheidung (CCVD) formuliert. Dieses Modell basiert hauptsächlich auf der Oberflächendiffusion von adsorbierten Kohlenstoffverbindungen entlang der Seitenwände der Nanoröhren sowie auf der Oberfläche der Katalysatorunterlage. Das Modell ist eine wichtige Ergänzung zu dem VLS-Mechanismus. Ein Wachstumsverfahren zur Herstellung von Nanoröhren für niedrigere Temperaturen bis zu 600 °C wurde entwickelt. Experimentell wurde nachgewiesen, dass der Durchmesser des Katalysatorteilchens fast ausschließlich bestimmt, wie viele Schalen eine wachsende Nanoröhre bei geeigneten Wachstumsbedingungen hat. Es wurde zum ersten Mal gezeigt, dass einschalige Kohlenstoffnanoröhren auf Metallelektroden wachsen werden können, insofern eine dünne Aluminiumschicht als Trennschicht verwendet wird. Dadurch können in-situ kontaktierte Nanoröhren einfach hergestellt werden, was deren elektrische Charakterisierung weitaus erleichtert. Mittels stromloser Abscheidung von Nickel oder Palladium aus einer Lösung konnte eine deutliche Verbesserung der Kontaktwiderstände der in-situ-kontaktierten Nanoröhren erreicht werden. Durch Einbettung von Nanoröhren in eine Tantaloxidschicht konnten Transistoren mit einem Dielektrikum mit hoher relativer Dielektrizitätskonstante hergestellt werden. Die Tantaloxidschicht wurde mit einem neu entwickelten Tauchprozess abgeschieden. Erstmalig wurden Transistoren basierend auf Kohlenstoffnanoröhren hergestellt, die relativ hohe Ströme (Milliampere) mit einer Modulation bis zu einem Faktor 500 schalten können. Diese Transistoren beruhen auf einer Parallelschaltung einer großen Anzahl an Nanoröhren. Mit Hilfe der hergestellten Transistoren konnten die Eigenschaften einer großen Zahl von Nanoröhren untersucht werden, wobei große Unterschiede in den elektronischen Eigenschaften von metallischen Nanoröhren, halbleitenden Nanoröhren und Nanoröhren mit einer kleinen Bandlücke beobachtet wurdenA number of very important growth and integration aspects of carbon nanotubes have been investigated during the course of this thesis. The focus was mainly on single-walled carbon nanotubes. Their potential for transistor applications was demonstrated by the successful fabrication of a variety of devices using rather simple processes. A detailed understanding of the dependence of SWCNT growth on a variety of parameters was obtained as the result of several thousand growth experiments. Various catalyst materials, gaseous carbon sources, and catalyst supports have been investigated. Special attention was paid to a considerable reduction of the growth temperature. A simple phenomenological growth model could be derived for CCVD of SWCNTs taking into account a number of effects observed during the various growth experiments. The model presented is mainly based on the surface diffusion of carbon species along the sidewalls of the carbon nanotubes or on the catalyst support and is an addition to the vapor-liquid-solid (VLS) mechanism. Growth methods for the CCVD synthesis of SWCNTs were developed for temperatures as low as 600 °C. It has been found that the size of the catalyst particle alone determines whether a SWCNT, DWCNT, or MWCNT will nucleate from a specific particle under suitable growth conditions. It could be demonstrated for the first time that SWCNTs can be grown on a variety of conducting materials if the catalyst is separated from the electrode by a thin Al layer. In-situ contacted SWCNTs can be easily obtained that way, largely facilitating the electronic characterization of as-grown SWCNTs. A tremendous improvement of the contacts of in-situ contacted SWCNTs could be achieved by electroless deposition. SWCNT growth on appropriate electrodes allowed the encapsulation of the nanotubes by electroless deposition of Ni and Pd, yielding good and reliable contacts. SWCNT transistors with a high-k dielectric could be fabricated by encapsulation of the nanotube with a tantalum oxide layer. The tantalum oxide was deposited by a newly developed dip-coat process. High-current SWCNT transistors consisting of a large number of SWCNTs in parallel were demonstrated for the first time during this work. Finally, the properties of a large number of CCVD grown SWCNTs have been investigated by electronic transport measurement. Large differences in the electronic transport have been observed for metallic, small band gap semiconducting (SGS), and semiconducting SWCNTs with small diameters
18
Bell, Chris. "Nanoscale Josephson devices." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/34607.
Full textAbstract:
This thesis describes the development and applications of sub-micron current-perpendicular-to plane devices fabricated by three-dimensional etching with a focused ion beam microscope. This technique was applied to a range of materials, including the study of c-axis Josephson junctions in the high temperature superconductor Tl2Ba2CaCu2O8, the fabrication of superconducting quantum interference devices with sub-micron loop areas, and GaN light emitting diodes. The main body of research was carried out in the study of Nb based Josephson junctions working at a temperature of 4.2 K. Junctions with normal metal, insulating and ferromagnetic barriers were characterised, as well as the first metallic antiferromagnetic Josephson junctions using γ-Fe50Mn50 as the barrier. 'Pseudo-spin-valve' Josephson junctions were also created using aCo/Cu/Fe20Ni80 barrier. In this case the relative orientation of the magnetic moments of the Co and Fe20Ni80 could be changed with an applied magnetic field. The magnetoresistance and critical current of the device showed a strong correlation, implying a direct influence of the magnetic structure of the device on the critical current.
19
Karabiyik, Mustafa. "Terahertz Plasmonic Devices." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3185.
Full textAbstract:
Terahertz (THz) devices are designed to operate from 0.1-10 THz. The THz spectra have unique properties such as penetration through soft materials and reflecting from hard materials, which make THz technologies, a prime candidate for imaging. Plasmons are longitudinal charge oscillations in carrier rich materials. Plasmons can be generated over the channel of transistors inducing a voltage between the source-drain when conditions are satisfied. In this thesis, plasmonic devices operating in the THz region have been studied both theoretically and experimentally investigating GaN/AlGaN and Graphene based transistors.
First, we report on a detailed study of dispersion properties of uniform grating gate THz plasmonic crystals, asymmetric dual grating gate plasmonic crystals and with symmetry-breaking defect-like cavities in order to understand the physics behind THz plasmons. For the first time, we defined the dispersion of plasmons in terms of effective plasmonic index. By adding an additional grating on top of the grating gate with a different periodicity, doubles the amount of absorption. Plasmons can be excited when polarization is perpendicular to the gate. We then showed focusing and exciting of THz plasmons polarization independent using circular grating lenses. Sub-micron THz ring resonators are presented showing THz guiding in plasmonic waveguides.
So far, resonant sensing has been observed only at cryogenic temperatures since electron mobility is high enough at low temperatures to sustain resonant plasmonic excitation at the channel of the detector. Recently, graphene attracted the attention of the researchers because of its high mobility at room temperature. Room temperature detection has been attempted and achieved, however the detectors have very small responsivity with non-resonant behavior since the graphene is sandwiched and fabrication of such detectors in large scale is impossible with the methods used. Here, we present a resonant room temperature detection of THz with upside down free standing graphene FETs having more than a 400 quality factor, a record high number in the field which is up to 50 times higher than GaN detectors and hundreds of responsivity values with a maximum around 400 V/W which is record high for graphene (10,000 times higher than previously reported graphene detector).
20
Myrén, Niklas. "Poled fiber devices /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262.
Full text
21
Baigent, Derek Ralph. "Polymer electroluminescent devices." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296712.
Full text
22
Bruna, Magali. "Piezoelectric ceramic devices." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615866.
Full text
23
Genot, Anthony. "DNA autonomous devices." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543551.
Full text
24
Pipe, Kevin P. (Kevin Patrick) 1976. "Bipolar thermoelectric devices." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16614.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 124-133).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
The work presented here is a theoretical and experimental study of heat production and transport in bipolar electrical devices, with detailed treatment of thermoelectric effects. Both homojunction and heterojunction devices are considered, and particular attention is given to semiconductor laser diodes. The mechanisms that govern both internal heat exchange and heat transfer between a device and its environment are examined, leading to structures which are optimized for thermal management.
by Kevin Patrick Pipe.
Ph.D.
25
Sethi, Sanjit (Sanjit Singh) 1971. "Grey man devices." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/70352.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.Includes bibliographical references (leaves 33-34).
The Vision Slaved to Walking Device i s one in a series of devices that are a result of the experimental ambulation series. The ability to see only when one's feet are moving allows for a distorted perspective of ones own perceptual world as well as the outside environment . The device is made up of precision electronic shutter systems, controllers, and foot switches. The larger goal of this and other projects in the experimental ambulation series is to re-establish connections with my perceptive systems to the outside world in order to remove my personal sensibility of numbness that I feel. experimental ambulation represents a series of attempts at distorting , altering, manipulating, and reshaping sensation and perception while walking. Each attempt has lead a following attempt applying information gained in order to further involve the next walking experiment . Often the stranger is someone who walks, both out of necessity and desire. With this in mind I engage the realm of the urban ambulatory environment. It is during this state , this state of not running and not standing still, that provides for fertile territory for the observation , re - arrangement , and re - formulation of difference aspects of the city. The desire to interact with the ground plane, with the city, with walking in non-traditional manners has necessitated the need for different strategies . Part performative, part fabrication , part documentation, and part social scientist these modes of operation are driven out of a desire to subvert and reexamine the world around me.
by Sanjit Sethi.
S.M.
26
Seidel, Robert Viktor. "Carbon Nanotube Devices." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24460.
Full textAbstract:
Eine Reihe wichtiger Wachstums- und Integrationsaspekte von Kohlenstoff-Nanoröhren wurde im Rahmen dieser Arbeit untersucht. Der Schwerpunkt der experimentellen Arbeit lag dabei hauptsächlich bei einschaligen Kohlenstoffnanoröhren (SWCNT). Das große Potential dieser Nanoröhren für Transistor-Anwendungen wurde durch die Herstellung einer Vielzahl funktionierender Bauelemente aus diesen Kohlenstoffnanoröhren mittels relativ einfacher Herstellungsprozesse demonstriert. Ein fundiertes Verständnis für die Abhängigkeiten des Nanoröhrenwachstums von einer Vielzahl an Parametern wurde mit Hilfe mehrerer tausend Wachstumsexperimente gesammelt. Verschiedene Katalysatormetalle, Kohlenstoffquellen und Katalysatorunterlagen wurden detailliert untersucht. Ein Hauptaugenmerk wurde dabei auf eine Reduzierung der Wachstumstemperatur gerichtet. Die niedrige Wachstumstemperatur spielt eine große Rolle für eine möglichst hohe Kompatibilität mit konventionellen Herstellungsverfahren der Silizium-Halbleitertechnik. Ein einfaches phänomenologisches Wachstumsmodell wurde für die Synthese von Nanoröhren mittels katalytisch-chemischer Gasphasen-Abscheidung (CCVD) formuliert. Dieses Modell basiert hauptsächlich auf der Oberflächendiffusion von adsorbierten Kohlenstoffverbindungen entlang der Seitenwände der Nanoröhren sowie auf der Oberfläche der Katalysatorunterlage. Das Modell ist eine wichtige Ergänzung zu dem VLS-Mechanismus. Ein Wachstumsverfahren zur Herstellung von Nanoröhren für niedrigere Temperaturen bis zu 600 °C wurde entwickelt. Experimentell wurde nachgewiesen, dass der Durchmesser des Katalysatorteilchens fast ausschließlich bestimmt, wie viele Schalen eine wachsende Nanoröhre bei geeigneten Wachstumsbedingungen hat. Es wurde zum ersten Mal gezeigt, dass einschalige Kohlenstoffnanoröhren auf Metallelektroden wachsen werden können, insofern eine dünne Aluminiumschicht als Trennschicht verwendet wird. Dadurch können in-situ kontaktierte Nanoröhren einfach hergestellt werden, was deren elektrische Charakterisierung weitaus erleichtert. Mittels stromloser Abscheidung von Nickel oder Palladium aus einer Lösung konnte eine deutliche Verbesserung der Kontaktwiderstände der in-situ-kontaktierten Nanoröhren erreicht werden. Durch Einbettung von Nanoröhren in eine Tantaloxidschicht konnten Transistoren mit einem Dielektrikum mit hoher relativer Dielektrizitätskonstante hergestellt werden. Die Tantaloxidschicht wurde mit einem neu entwickelten Tauchprozess abgeschieden. Erstmalig wurden Transistoren basierend auf Kohlenstoffnanoröhren hergestellt, die relativ hohe Ströme (Milliampere) mit einer Modulation bis zu einem Faktor 500 schalten können. Diese Transistoren beruhen auf einer Parallelschaltung einer großen Anzahl an Nanoröhren. Mit Hilfe der hergestellten Transistoren konnten die Eigenschaften einer großen Zahl von Nanoröhren untersucht werden, wobei große Unterschiede in den elektronischen Eigenschaften von metallischen Nanoröhren, halbleitenden Nanoröhren und Nanoröhren mit einer kleinen Bandlücke beobachtet wurden.A number of very important growth and integration aspects of carbon nanotubes have been investigated during the course of this thesis. The focus was mainly on single-walled carbon nanotubes. Their potential for transistor applications was demonstrated by the successful fabrication of a variety of devices using rather simple processes. A detailed understanding of the dependence of SWCNT growth on a variety of parameters was obtained as the result of several thousand growth experiments. Various catalyst materials, gaseous carbon sources, and catalyst supports have been investigated. Special attention was paid to a considerable reduction of the growth temperature. A simple phenomenological growth model could be derived for CCVD of SWCNTs taking into account a number of effects observed during the various growth experiments. The model presented is mainly based on the surface diffusion of carbon species along the sidewalls of the carbon nanotubes or on the catalyst support and is an addition to the vapor-liquid-solid (VLS) mechanism. Growth methods for the CCVD synthesis of SWCNTs were developed for temperatures as low as 600 °C. It has been found that the size of the catalyst particle alone determines whether a SWCNT, DWCNT, or MWCNT will nucleate from a specific particle under suitable growth conditions. It could be demonstrated for the first time that SWCNTs can be grown on a variety of conducting materials if the catalyst is separated from the electrode by a thin Al layer. In-situ contacted SWCNTs can be easily obtained that way, largely facilitating the electronic characterization of as-grown SWCNTs. A tremendous improvement of the contacts of in-situ contacted SWCNTs could be achieved by electroless deposition. SWCNT growth on appropriate electrodes allowed the encapsulation of the nanotubes by electroless deposition of Ni and Pd, yielding good and reliable contacts. SWCNT transistors with a high-k dielectric could be fabricated by encapsulation of the nanotube with a tantalum oxide layer. The tantalum oxide was deposited by a newly developed dip-coat process. High-current SWCNT transistors consisting of a large number of SWCNTs in parallel were demonstrated for the first time during this work. Finally, the properties of a large number of CCVD grown SWCNTs have been investigated by electronic transport measurement. Large differences in the electronic transport have been observed for metallic, small band gap semiconducting (SGS), and semiconducting SWCNTs with small diameters.
27
Trebula, Peter. "Mobile Devices Attacks." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2007. http://www.nusl.cz/ntk/nusl-236912.
Full textAbstract:
Táto práca sa zaoberá bezpečnostnými architektúrami v mobilných zariadeniach a rôznymi formami útokov proti nim. V prvej časti je úvod do bezpečnosti mobilných zariadení a bezpečnostné riziká súvisiace s mobilnými zariadeniami. Sú tu uvedené slabé miesta vo WLAN sieťach a úvod do Bluetooth technológie aj s rizikami. V druhej časti je predstavenie produkčného testovania, ktoré sa využíva u spoločnosti Nokia a popis jednotlivých testov používaných na vyskúšanie funkčnosti zariadení. Rovnako sa v nej nachádza popis architektúry, ktorou sú mobilné zariadenia u spoločnosti Nokia zabezpečené voči rôznym formám útokov viažucim sa na inštalovanie softwaru a testovanie.
28
JASMIN, ALLADIN. "Oxide Memristive Devices." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2639136.
Full textAbstract:
Resistive switching in metal oxide materials has recently renewed the interest of many researchers due to the many application in non-volatile memory and neuromorphic computing. A memristor or a memristive device in general, is a device behaving as nonlinear resistor with memory which depends on the amount of charges that passes through it. A novel idea of combining the physical resistive switching phenomenon and the circuit-theoretic formalism of memristors was proposed in 2008. The physical mechanism on how resistive switching occurs is still under debate. A physical understanding of the switching phenomenon is of much importance in order to tailor specific properties for memory applications. To investigate the resistive switching in oxide materials, memristive devices were fabricated starting from materials processing: low-pressure chemical vapor deposition of ZnO nanowires (NWs), low-temperature atomic layer deposition (ALD) of TiO2 thin films and micro-pulse ALD of Fe2O3 thin films. The distinct geometry of ZnO NWs makes it possible to investigate the effect of the electrode material, surface states and compliance to the memristive properties. A simpler method of fabricating TiO2-based devices was explored using low-temperature atomic layer deposition. This approach is very promising for device application using photoresist and polymeric substrates without thermal degradation during and after device fabrication. ALD of pure phase Fe2O3 thin films was demonstrated using cyclic micro-pulses. Based on the performance of the fabricated devices, the oxide materials under this study have promising properties for the next-generation memory devices.
29
Fiorini, Gina S. "Polymeric microfluidic devices : development of thermoset polyester microfluidic devices and use of poly(dimethylsiloxane) devices for droplet applications /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8627.
Full text
30
Yang, Nanying. "Characterization and modeling of silicon and silicon carbide power devices." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/29643.
Full textAbstract:
Power devices play key roles in the power electronics applications. In order for the power electronics designers to fully utilize the performance advantages of power devices, compact power device models are needed in the circuit simulator (Saber, P-spice, etc.). Therefore, it is very important to get accurate device models. However, there are many challenges due to the development of new power devices with new internal structure and new semiconductor materials (SiC, GaN, etc.).
In this dissertation, enhanced power diode model is presented with an improvement in the reverse blocking region. In the current power diode model in the Saber circuit simulator, an empirical approach was used to describe the low-bias reverse blocking region by introducing an effect called â conduction loss,â a parameter that causes a linear relationship between the device voltage and current at low bias voltages with no physics meaning. Furthermore, this term is not sufficient to accurately describe the changes to the device characteristics as the junction temperature is varied. In the enhanced model, an analytical temperature dependent model for the reverse blocking characteristics has been developed for Schottky/JBS diodes by including the thermionic-emission mechanism in the low-bias range. The newly derived model equations have been implemented in Saber circuit simulator using MAST language. An automated parameter extraction software package developed for constructing silicon (Si) and silicon carbide (SiC) power diode models, which is called DIode Model Parameter extrACtion Tools (DIMPACT). This software tool extracts the data necessary to establish a library of power diode component models and provides a method for quantitatively comparing between different types of devices and establishing performance metrics for device development.
This dissertation also presents a new Saber-compatible approach for modeling the inter-electrode capacitances of the Si CoolMOSTM transistor. This new approach accurately describes all three inter-electrode capacitances (i.e., gate-drain, gate-source, and drain-source capacitances) for the full operating range of the device. The model is derived using the actual charge distribution within the device rather than assuming a lumped charge or one-dimensional charge distribution. The comparison between the simulated data with the measured results validates the accuracy of the new physical model.Ph. D.
31
Halberg, David. "Teaching Devices in Education : Focusing on Technical Devices in Spanish Teaching." Thesis, Jönköping University, JIBS, Business Informatics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-6730.
Full textAbstract:
The aim of the thesis is to investigate how teaching devices, with focus on ICT use are regarded in education. I make comparison with teaching without technical devices, but emphasize the teaching with such devices. I address questions concerning what technical devices are used and in which way these devices may enhance the education process. In addition, in which way the devices influence power and communication.
The methods indicate a deductive-abductive approach, observations, interviews, and questionnaires. The theoretical framework focuses, Linguistics, Pedagogy, cognition, and Informatics. The results-part is built up on two cases – one concerning teaching with technical devices, the other concerning teaching without those devices. The results imply that the schools of Sweden use computers and Internet in a very ‘common’ way. However, there are intentions to use cell phones with software to assist the teaching. By this approach, that would be possible to add an additional time to the lectures since the pupils and teachers can work outside the classroom. One problem with technical devices is named ‘noise’, which are things in between the ‘useful’ (technical) devices and issues around that can decrease the learning process. In addition; if the goal is to have a symmetrical relationship between teacher and pupil, it may be difficult without taking carefully account on the (technical) device in use, and perhaps regard them as cognitive tools. From what I found, the tools are not regarded as cognitive.
32
Spilker, Mark H. (Mark Henry) 1971. "Peripheral nerve regeneration through tubular devices : a comparison of assays of device effectiveness." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9091.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (leaves 143-148).
Peripheral nerve injury affects nearly 200,000 patients annually in the United States and unless treated results in paralysis of skeletal muscle and loss of sensation. Previous studies in this laboratory have focused on comparing the effectiveness of various tubular devices in repairing experimental nerve injuries in an animal model. The devices were rank-ordered based on clinically relevant assays of regeneration such as number regenerated nerve fibers and electrophysiological conduction properties of the regenerated nerves. Such assays provide a useful measure of the clinical efficacy of devices but require long-term (up to 60-week) studies in order to obtain meaningful results. There exists a need for a short-term (less than 12-week) assay with which nerve repair devices can be compared. The overall goal of this thesis was to establish an experimental assay that can be used to detect statistically significant differences among nerve repair devices in short-term studies. In this thesis, four different assays of nerve regeneration were compared on the basis of their appropriateness to quantify the regeneration promoted by nerve repair devices in studies less than 12 weeks in duration. An acceptable assay must reach a plateau with time during short-term studies and must yield a quantitative metric with which nerve devices can be compared. The results of this thesis suggest that an assay based on ability of a nerve repair device to promote reinnervation across nerve gaps of various lengths meets the criteria for an acceptable assay. The data also indicate that the characteristic gap length (Lc), which is derived from curve-fitting the experimental data for reinnervation versus gap length, can be used as a quantitative metric of nerve regeneration. The experimental data indicate that for the silicone tube device, the value of Lc reached a plateau with time before 9 weeks, and the standard error in L was less than 5 percent of the value in two different nerve repair models (single-leg and crossanastomosis). The data also suggest that statistically significant differences between the silicone tube device and a collagen-based device (the CG device) are obtainable during short-term (12-week) studies.
by Mark H. Spilker.
Ph.D.
33
Pavesi, Alessandro. "Design and implementation of a Reinforcement Learning framework for iOS devices." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25811/.
Full textAbstract:
Reinforcement Learning is an increasingly popular area of Artificial Intelligence. The applications of this learning paradigm are many, but its application in mobile computing is in its infancy. This study aims to provide an overview of current Reinforcement Learning applications on mobile devices, as well as to introduce a new framework for iOS devices: Swift-RL Lib. This new Swift package allows developers to easily support and integrate two of the most common RL algorithms, Q-Learning and Deep Q-Network, in a fully customizable environment. All processes are performed on the device, without any need for remote computation. The framework was tested in different settings and evaluated through several use cases. Through an in-depth performance analysis, we show that the platform provides effective and efficient support for Reinforcement Learning for mobile applications.
34
Ayesh, Ahmad Ibrahim. "Device fabrication using Bi nanoclusters." Thesis, University of Canterbury. Phsics and Astronomy, 2007. http://hdl.handle.net/10092/3272.
Full textAbstract:
Nanoclusters have special importance in nanotechnology because of their low dimensionality, which provides electronic, chemical, and magnetic properties that differ from those of the equivalent bulk materials. Suitably controllable self-assembly methods are required in order to incorporate nanoclusters into useful devices. The self-assembly method used in this study employs V-grooves as a template element for nanocluster device fabrication. The V-grooves are fabricated by optical lithography on SiO2/Si wafers and KOH wet etching. Bi clusters deposited on a V-groove form a self-assembled conducting wire. The clusters are produced using an inert gas aggregation source inside an ultra high vacuum compatible system. In order to characterise the assembly process, Bi clusters with different average sizes and velocities are deposited on V-grooves with different widths. The cluster bouncing was found to be the main process in forming the cluster wires. The bouncing angles were smaller than the incident angle, and they are dependent on the cluster size and velocity. For a certain bouncing angle, the wire width reflects the V-groove width because of the fixed bouncing angle. Nanocluster devices were fabricated by depositing the clusters on V-grooves with pre-formed Au/NiCr electrical contacts. The amount of the deposited material required to form an electrically conducting wire was found to be a function of the V-groove width and the wire length. The two point I(V) measurements in the voltage range between -1 and +1V showed linear characteristics for low resistance wires (kΩ), and non-linear characteristics for the high resistance ones (MΩ). The silicon substrate was used as a back gate. Applying a voltage to the gate was found to modify the electrical conduction of the cluster wire. The temperature dependence of the resistance of the nanocluster wires was studied in the temperature range of 4.2-473K, and all of the measured wires showed a negative temperature coefficient of resistance. These measurements allowed a detailed study of the conduction mechanisms through the cluster wires. The study showed that Bi clusters can be used for device fabrication. To size select the clusters prior to using them for the device fabrication, a high transmission mass filter is required. This transmission can be obtained using the von Issendorff and Palmer mass filter if it is operated using the optimum operation conditions. The mass filter consists of two pairs of parallel plates with horizontal openings in Plates 1 and 2, and it operates on the time of flight principle. During this project, the operation conditions of this mass filter were studied using both experiment and simulation. The study showed that the beam deflection angle is a critical factor in optimising the mass filter transmission efficiency. This angle is dependent on the accelerating voltage, ion mass, and the horizontal velocity of the ions. The optimum operation conditions for the mass filter were found and used to study the mass distribution of Pd ions produced by a magnetron sputtering source with variable cluster aggregation length.
35
Mangelinckx, Glenn. "Investigation of nanophotonic devices based on transformation optics : Transforming reflective optical devices." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-42442.
Full textAbstract:
Transformation optics (TO), which provides an elegant way of molding the flow of light to one's wishes, has become one of the most popular photonics research areas during the last few years. Owing to stringent material parameters of transformation media, TO is in general not favourable for designing practical applications. The recent proposal of carpet cloak, a device that optically hides an anomaly on an otherwise at reflective surface, simplifies material requirements due to the relaxed boundary condition on the cloak's reflective border, thus providing the prospect of realization at optical wavelength. In light of this approach, this thesis introduces a general procedure for transforming reflective optical devices, including in particular focal mirrors and diraction gratings. The curved or zigzagged surfaces of such devices are attened through a smooth coordinate mapping which makes convenient use of the loose boundary conditions on the reflective surface. The resulting devices are transformation media without extreme material parameters. For two-dimensional structures, it is even possible to attain an approximate dielectric-only implementation when considering only transverse-electric or transverse-magnetic incidence. The flattened reflective devices are finally adapted to operate in a transmission mode, creating focal lenses and transmissive diffraction gratings. It is illustrated through full-wave simulation that the performance of these transformation optical devices - under the right circumstances also for the dielectric only implementations - surpasses their traditional equivalents.
36
Nyberg, Tobias. "Nano and micro patterned organic devices : from neural interfaces to optoelectronic devices /." Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek750s.pdf.
Full text
37
Subannajui, Kittitat [Verfasser], and Margit [Akademischer Betreuer] Zacharias. "ZnO nanowires : : fabrication, properties and devices = ZnO-Nanodrähten Herstellung : Eigenschaften und Devices." Freiburg : Universität, 2011. http://d-nb.info/112346040X/34.
Full text
38
Willfahrt, Andreas. "Screen Printed Thermoelectric Devices." Licentiate thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-106006.
Full textAbstract:
Thermoelectric generators (TEG) directly convert heat energy into electrical energy. The impediments as to why this technology has not yet found extensive application are the low conversion efficiency and high costs per watt. On the one hand, the manufacturing process is a cost factor. On the other, the high-‐priced thermoelectric (TE) materials have an enormous impact on the costs per watt. In this thesis both factors will be examined: the production process and the selection of TE materials. Technical screen printing is a possible way of production, because this method is very versatile with respect to the usable materials, substrates as well as printing inks. The organic conductor PEDOT:PSS offers reasonable thermoelectric properties and can be processed very well in screen printing. It was demonstrated by prototypes of fully printed TEGs that so-‐called vertical printed TEGs are feasible using standard graphic arts industry processes. In addition, the problems that occur with print production of TEGs are identified. Finally, approaches to solve these problems are discussed.
39
Crossley, Samuel. "Electrocaloric materials and devices." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/245063.
Full textAbstract:
The temperature and/or entropy of electrically polarisable materials can be altered by changing electric field E. Research into this electrocaloric (EC) effect has focussed on increasing the size of the EC effects, with the long-term aim of building a cooler with an EC material at its heart. Materials and experimental methods are briefly reviewed. A ‘resetting’ indirect route to isothermal entropy change ∆S for hysteretic first-order transitions is described. An indirect route to adiabatic temperature change ∆T, without the need for field-resolved heat capacity data, is also described. Three temperature controllers were built: a cryogenic probe for 77-420 K with ∼5 mK resolution, a high-temperature stage with vacuum enclosure for 295-700 K with ∼15 mK resolution, and a low-temperature stage for 120-400 K with electrical access via micropositioners. Automation enables dense datasets to be compiled. Single crystals of inorganic salts (NH4)2SO4 , KNO3 and NaNO2 were obtained. Applying 380 kV cm−1 across (NH4)2SO4 , it was found that |∆S| ∼ 20 J K−1 kg−1 and |∆T | ∼ 4 K, using the indirect method near the Curie temperature TC = 223 K. Without the ‘resetting’ indirect method, |∆S| ∼ 45 J K−1 kg−1 would have been spuriously found. Preliminary indirect measurements on KNO3 and NaNO2 give |∆S| ∼ 75 J K−1 kg−1 for ∆E ∼ 31 kV cm−1 near TC = 400 K and |∆S| ∼ 14 J K−1 kg−1 for ∆E ∼ 15 kV cm−1 near TC = 435 K, respectively. A cation-ordered PbSc0.5Ta0.5O3 ceramic showing a nominally first-order transition at 295 K was obtained. The Clausius-Clapeyron phase diagram is revealed via indirect measurements where |∆S| ∼ 3.25 J K−1 kg−1 and |∆T | ∼ 2 K, and direct measurements where |∆T | ∼ 2 K. Clamped samples show broadening of the field-induced transition. Epitaxial, ∼64 nm-thick SrTiO3 films were grown by pulsed laser deposition on NdGaO3 (001) substrates with a La0.67Sr0.33MnO3 bottom electrode. The indirect method gives |∆S| ∼ 8 J K−1 kg−1 and |∆T | ∼ 3.5 K near 180 K with |∆E| = 780 kV cm−1. Finite element modelling (FEM) was used to optimise the geometry of multilayered capacitors (MLCs) for EC cooling. Intrinsic cooling powers of 25.9 kW kg−1 are predicted for an optimised MLC based on PVDF-TrFE with Ag electrodes.
40
Reddick, William Michael. "Novel silicon tunnelling devices." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/251612.
Full text
41
Barlow, Iain J. "Nanostructured Molecular Electronic Devices." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486548.
Full textAbstract:
Candidate organic semiconductor materials based on a,ro-dihexylquaterthiophene (dH4T) and a,ro-dihexylbis(phenylene)bithiophene (dHPTTP) core systems were synthesised. The tenninal positions of the alkyl substituents were substituted with, thioacetate, phosphonic acid, glycolic ester and allyl ether groups to enable the fonnation of self-assembled monolayers (SAMs) of the adsorbates onto Au, Ah03 and H-Si surfaces. These were then probed with x-ray photoelectron spectroscopy (XPS) and friction force microscopy (FFM). Analysis of the XPS spectra confirmed that the oligomers fonned monolayer films onto the respective substrates although the allyl-terminated oligomers were subject to oxidation when attached onto H-Si by thermally-initiated radical attachment. Comparison of this method with photochemical initiation highlighted a potentially competing photolysis reaction. FFM showed that the frictional properties of both the thiolate and phosphonic acid SAMs on Au and Ah03 for the oligomers depended on both the tail group polarity and the density of packing for the adsorbates, whilst the allyl-capped materials formed disordered monolayers on H-Si. Chemical patterns of the thioacetate and phosphonic acid-terminated oligomers were produced by the irradiation of methyl-tenninated alkanethiols and alkylphosphonic acids with 244 nm UV light. The irradiation and subsequent displacement of the exposed adsorbates with the dH4T and dHPTTP-based thioactetates and phosphonic acids resulted in areas of relatively high and low friction, which was imaged by FFM. The SAM photomodification process on Ah03 was monitored by XPS, and suggested C-P bond photolysis as a potential mechanism. Scanning near-field photolithography (SNP) was then used to generate dH4T and dHPTTP features into alkanethiol and phosphonate SAMs. The smallest features, of 40 nm fwhm demonstrate that SNP is a viable method for the preparation of organic semiconductors with nanometre resolution, with potential application in the production of self-assembled monolayer field-effect transistors (SAMFETs).
42
Al-Amin, Chowdhury G. "Advanced Graphene Microelectronic Devices." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2512.
Full textAbstract:
The outstanding electrical and material properties of Graphene have made it a promising material for several fields of analog applications, though its zero bandgap precludes its application in digital and logic devices. With its remarkably high electron mobility at room temperature, Graphene also has strong potential for terahertz (THz) plasmonic devices. However there still are challenges to be solved to realize Graphene’s full potential for practical applications.
In this dissertation, we investigate solutions for some of these challenges. First, to reduce the access resistances which significantly reduces the radio frequency (RF) performance of Graphene field effect transistors (GFETs), a novel device structure consisting of two additional contacts at the access region has been successfully modeled, designed, microfabicated/integrated, and characterized. The additional contacts of the proposed device are capacitively coupled to the device channel and independently biased, that induce more carriers and effectively reduce access resistance.
In addition to that, in this dissertation, bandgap has been experimentally introduced to semi-metallic Graphene, by decorating with randomly distributed gold nano-particles and zinc oxide (ZnO) nano-seeds, where their interaction breaks its sublattice symmetry and opens up bandgap. The engineered bandgap was extracted from its temperature dependent conductivity characteristics and compared with reported theoretical estimation. The proposed method of device engineering combined with material bandgap engineering, on a single device, introduces a gateway towards high speed Graphene logic devices.
Finally, THz plasmon generation and propagation in Graphene grating gate field effect transistors and Graphene plasmonic ring resonators have been investigated analytically and numerically to explore their potential use for compact, solid state tunable THz detectors.
43
Reichel, René. "Nano Scale Cluster Devices." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1385.
Full textAbstract:
This study uses clusters formed in a UHV-compatible cluster apparatus, which was built and commissioned during this thesis. The design and operation of the cluster deposition system is described. This system is optimised for high clus- ter fluxes and for the production of cluster assembled nanoscale devices. One key feature of the system is a high degree of flexibility, including interchangeable sputtering and inert gas aggregation sources, and two kinds of mass spectrome- ter, which allow both characterisation of the cluster size distribution and deposi- tion of mass-selected clusters. Another key feature is that clusters are deposited onto electrically contacted lithographically defined devices mounted on an UHV- compatible cryostat cold finger, allowing deposition at room temperature as well as at cryogenic and at elevated temperatures. The electrically contacted nanoscale cluster devices were fabricated using a novel template technique. Hereby, clusters are placed between two electrodes separated only by ∼100 nm. The width of the cluster ensemble is in the order of a few cluster diameters, which means that the assembled clusters form a cluster wire bridging the electrode separation. During this thesis, the design and layout has been optimised to be able to measure electrical properties of the cluster devices and in particular to investigate the interaction between the cluster ensemble and the contact electrodes. In-situ electrical characterisation of cluster assembled nanoscale devices are performed in the temperature range 4.2 K to 375 K. The samples are provided with a backgate, which in principle allows modification of the conduction through the cluster ensemble by applying a gate voltage. However, no change in conduc- tion with changes in gate voltages was seen. The main focus of the electrical measurements is on the current voltage char- acteristics. It was noticed that the nanoscale bismuth (and antimony) cluster devices exhibited non-linear current voltage characteristics, which were in stark contrast to the linear current voltage characteristics measured for cluster films previously. Investigations into the causes of this non-linearity suggests that tun- nelling conduction occurs between the cluster ensemble (wire) and the contact electrodes. The non-linear current voltage characteristics were fitted using three models of tunnelling conduction and appear to be best fitted using a model in- volving fluctuation-assisted tunnelling through barriers of different heights. Further, measurements of the temperature dependent resistance are performed showing an increase of resistance with decreasing temperature for bismuth and antimony assembled cluster devices. The temperature dependence of bismuth as- sembled cluster wires can be explained by the decrease of the carrier concentration in bismuth for decreasing temperature. Annealing of the cluster ensemble and the cluster contact connection resulted in an increase in conduction. This increase of conduction can be explained due to the current flow through the cluster wire. Locally, at the bottlenecks, the current flow causes resistive heating and subsequently coalescence of two (or more) clusters.
44
Omojokun, Olufisayo Dewan Prasun. "Interacting with networked devices." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,174.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). " ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Computer Science." Discipline: Computer Science; Department/School: Computer Science.
45
Chiu, Pit Ho Patrio 1977. "Bismuth based nanoelectronic devices." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100337.
Full textAbstract:
Bismuth (Bi) is a unique electronic material with small effective mass (∼0.001me) and long carrier mean free path (100 nm at 300K). It is particularly suitable for studying nano scale related phenomena such as size effect and energy level spacing. In this thesis work, bismuth based nanoelectronic devices were studied. Devices were fabricated using a combination of electron beam (e-beam) writing and thermal evaporation techniques. Dimensions of the fabricated devices were in the order of 100 rim. All structures were optimized for individual electrical characterization. Three types of devices were studied: Bi nanowires, Bi nanowires with dual side-gate structures and Bi nanodot structures. In the study of Bi nanowires, metal-to-semiconductor transition phenomenon and size effect were observed. The conduction behavior of Bi nanowires changed from metallic to semiconductor when the device's critical dimension was reduced to below 50 nm. It is a solid experimental evidence of the quantum confinement-induced bandgap theory. Additionally, it has been found in the present work that resistivity of individual Bi nanowire increased as linewidth decreased indicating size effect occurred in the Bi nanowires. Dual side-gate structures were formed adjacent to the Bi nanowires in an attempt to modulate the current. Measurements showed a 7% of current modulation. The small current modulation suggested the high carrier density in the nanowire which has prevented the full depletion of free carriers. 100 nm-diameter Bi nanodot structures were fabricated utilizing proximity effect of e-beam writing. Precise control of electron doses and process conditions led to the successful fabrication of sub-nanometer tunneling junctions to the nanodots. Significant non-linear current-voltage (I-V) characteristic was observed at low temperatures. The step like I-V characteristic was a strong indication of energy level spacing in the zero-dimensional nanodot structure. The successful observation of energy level spacing in a relatively large nanodot is due to the small effective mass of bismuth material which leads to a measurable energy level spacing.
46
Imbers, Jara. "Dynamics of nanoelectromechanical devices." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490977.
Full textAbstract:
In this thesis we present a study of a particular type of nanoelectromechanical system which consists of a nanomechanical resonator coupled to a superconducting single electron transistor (SSET) in the vicinity of a current resonance known as the Josephson quasiparticle resonance.
47
Isaac, Stephen Paul. "Grain boundary perovskite devices." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604963.
Full textAbstract:
The perovskite family has many novel features including, in certain compounds, either high temperature superconductivity or colossal magnetoresistance (CMR). The electrical and magnetic properties of grain boundaries in these materials also have their own unique properties. These distinct characteristics can be exploited to make devices with a range of potential applications. In this thesis, two types of devices are presented. Superconducting grain boundaries have been studied extensively and can form Jospehson junctions. The grain boundaries have a reduced supercurrent but a substantially enhanced sensitivity to magnetic fields relative to the bulk material. As current in nearby control loops can generate magnetic flux in the grain boundary, Josephson vortex flow transistors can be made. The properties of one type of this device are presented as a function its shape and relative dimensions. Tapering the junction width is shown to produce a substantial current gain over a significant field range. These devices can be used as current based logic gates. In 1995, reports of the low magnetic field response in polycrystalline films of the CMR manganites were published. These low-field effects were attributed to the grain boundaries present in the granular materials. To isolate and maximise this response, a Wheatstone bridge structure has been patterned into various bicrystal CMR films. The properties of the grain boundaries are reported as a function of temperature, the magnitude and orientation of the magnetic field, and also as a function of the grain boundary angle. CMR grain boundaries may replace the giant magnetoresistive read heads which are the current state of the art in magnetic read head technology. The possibility of a common transport mechanism in these two types of materials has been explored and several similarities have been found to exist.
48
Alzubi, Feras. "Planar Organic Photovoltaic Devices." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5756.
Full textAbstract:
Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical structure limits one of the electrode to be a transparent electrode as well as introducing inseparable relation between the electrodes separation and the active material thickness. In addition, it is also well known that the charge transport in OSC is anisotropic and the charge mobility is better in lateral direction rather than vertical direction. In order to address some of these issues, we fabricated OPV devices in a planar device structure where cathode and anode of dissimilar metals are in-plane with each other and their photovoltaic behaviors were studied. We used poly(3-hexylthiophene) and [6,6]-pheny1 C61-butyric acid methy1 ester (P3HT:PCBM) blend as an active material. In particular, we present a detailed study about the effects of the structural parameters such as the channel length, the active layer thickness, and the work function of the electrodes on the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and the power conversion efficiency (PCE). In order to determine the suitable anode and cathode for the planar organic photovoltaic (P-OPV) structure, we first fabricated and measured organic field effect transistor (OFET) devices with different contacts and studied the effect of barrier height at the P3HT:PCBM/electrode interface on the device output and transport properties. The study showed a clear effect of varying the contact material on the charge injection mechanism and on the carriers mobilities. The results have also shown that Au with high hole mobility and on current in the p-channel can be used as an anode (holes extractor) in the P-OPV device while In, Cr, and Ti that showed a reasonable value of electron mobility can be good candidates for cathode (electron extractor). We also found that, Ag, Al, and Mg showed large barrier which resulted in large threshold voltage in the I-V curve making them undesired cathode materials in the P-OPV device. We then fabricated P-OPV devices with Au as an anode material and varied the cathode material to study the effect of the interface between the P3HT:PCBM layer and the cathode material. When Al, Mg, or Ag used as a cathode material no PV behavior was observed, while PV behavior was observed for In, Cr, and Ti cathode materials. The PV behavior and the characteristic parameters including Voc, Isc, FF and PCE were affected by varying the cathode material. The results have shown that the P-OPV device performance can be affected by the cathode material depending on the properties and the work function of the metal. We have also studied the effect of varying the P3HT:PCBM layer thickness at a fixed channel length for Cr and Ti cathode materials and Au as anode. While Voc and FF values do not change, Isc and PCE increase with increasing the layer thickness due to the increase of the light absorption and charges generation. Moreover, we studied the effect of varying the channel length at a fixed film thickness; and showed that the values of Isc and PCE increase with decreasing channel length while Voc and FF maintain the same value. In this thesis we will also present the results on experimentally defining and testing the illuminated area in the P-OPV device by using different measurement set-ups and different electrodes patterns. The results prove that the illuminated area in the P-OPV device is the area enclosed between the two electrodes. Lastly, we will present the effect of the P3HT:PCBM ratio on the P-OPV device performance. We show that 1:2 ratio is the optimized ratio for the P-OPV device. The detailed results in this thesis show a potential opportunity to help improving and understanding the design of OPV device by understanding the effects of the device structural parameters.Ph.D.
Doctorate
Physics
Sciences
Physics
49
Thompson, Paul. "II-VI optoelectronic devices." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/726.
Full text
50
Wang, Jue. "Silicon carbide power devices." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/579.
Full text