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Muntahi, Abdussamad. "NANOSCALE EFFECTS IN JUNCTIONLESS FIELD EFFECT TRANSISTORS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1527.
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Though the concept of junctionless field effect transistor (JLFET) is old, it was not possible to fabricate a useful JLFET device, as it requires a very shallow channel region. Very recently, the emergence of new and advanced technologies has made it possible to create viable JLFET devices using nanowires. This work aims to computationally investigate the interplay of quantum size-quantization and random dopant fluctuations (RDF) effects in nanoscale JLFETs. For this purpose, a 3-D fully atomistic quantum-corrected Monte Carlo device simulator has been integrated and used in this work. The size-quantiza¬tion effect has been accounted for via a param¬eter-free effec¬tive potential scheme and benchmarked against the NEGF approach in the ballistic limit. To study the RDF effects and treat full Coulomb (electron-ion and electron-electron) interactions in the real-space and beyond the Poisson picture, the simulator implements a corrected-Coulomb electron dynamics (QC-ED) approach. The essential bandstructure and scattering parameters (energy bandgap, effective masses, and the density-of-states) have been computed using an atomistic 20-band nearest-neighbour sp3d5s* tight-binding scheme. First, an experimental device was simulated to evaluate the validity of the simulator. Because of the small dimension, quantum mechanical confinement was found to be the dominant mechanism that significantly degrades the current drive capability of nanoscale JLFETs. Surface roughness scattering is not as prominent as observed in conventional MOSFETs. Also, because of its small size, the performance of the device is prone to the effect of variability, for which a discrete doping model was proved essential. Finally, a new JLFET was designed and optimized in this work. The proposed device is based on a gate-all-around silicon nanowire. Source/drain length is 32.5 nm and channel length is 14 nm. Gate contact length is 9 nm. The EOT (equivalent oxide thickness) is 1 nm. It has a metal gate with a workfunction of 4.55 eV. The source, channel and drain regions are n-type with a doping density of 1.5×1019 cm-3. Detailed simulation shows that the two most influential mechanisms that degrade the drive capability are quantum mechanical confinement and Coulomb scattering. Surface roughness scattering is found to be very weak. In addition, thinner nanowire is more prone to Coulomb scattering exhibiting a reduced ON-current (ION). Simulation results show that silicon nanowires with a side length (width and depth) of 3 nm and a doping density of 1.5×1019 cm-3 produce satisfactory drive current.
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Rawcliffe, Ruth. "Polymer field-effect transistors." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/8889.
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Georgakopoulos, Stamatis. "Polymer field-effect transistors." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582857.
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High Ionisation Potential (IP) amorphous conjugated polymers are very practical semiconductors and promising candidates for printing applications as they exhibit 1) high air-stability due to the high IP, and 2) reproducible electrical performance due to the uniformity of amorphous morphology. However they generally exhibit low mobilities on the order of 10-3 cm2Ns and below. This work is based mainly on two high-IP amorphous conjugated polymers poly(indenofluorene-triarylamine) (PIFTAA) and poly(indenofluorene- phenanthrene) (PIFPA). The long term ambient stability of PIFTAA and PIFPA with IPs of 5.45 eV and 5.79 eV respectively is characterised in Field-Effect Transistors (FETs) over a period of 4 and 2 months respectively. FET parameters such as the turn-on voltage and subthreshold slope are found to be generally stable, and the charge carrier mobility is found to degrade at an approximate rate of 10% per month, which is amongst the lowest reported values for organic semiconductors. PIFT AA and particularly PIFPA exhibit high field-effect saturation mobilities of 0.03 - 0.04 cm2Ns and 0.2 - 0.3 cm2Ns respectively, which are unusually high for amorphous conjugated polymers. The morphologies are examined by atomic force microscopy, grazing incidence wide angle x-ray scattering, and differential scanning calorimetry, and no evidence of crystallinity is detected, suggesting that the conjugated polymers are indeed amorphous. To investigate charge transport in PIFTAA and PIFPA, FETs of multiple channel lengths are fabricated, providing mobility data for multiple electric fields, and measured over a range of temperatures. In addition to PIFT AA and PIFP A, the measurements are performed on typical amorphous conjugated polymers poly(triarylamine) (PTAA) and poly(indenofluorene-triarylamine-triarylamine) (PIFTAATAA), with mobilities of 0.003 cm2/Vs and 0.004 cm2Ns respectively. The gate voltage dependence of the mobility extracted from FET measurements, as well as the lIT2 fit of the mobility with temperature is consistent with a Gaussian Density of States. The indenofluorene copolymers PIFTAA, PIFTAATAA, and PIFPA exhibit clear negative electric field dependence of the mobility, signature of high spatial disorder in the polymer films. The temperature dependence of the mobility is fed into the Gaussian Disorder Model, which indicates that the source of the high mobility for PIFPA is mainly strong intermolecular coupling indicated by the high pre-factor mobility as well as low energetic disorder along the path of charge flow. These results challenge the widely accepted concept that high crystallinity is a requirement for mobility exceeding 0.1 cm2/Vs in organic semiconductors.
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Chua, L. L. "Organic field-effect transistors." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597679.
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In this thesis, we demonstrated that divinyltetramethyldisiloxane-benzocyclobutene (BCB), which has previously been used as an isolation dielectric in III-IV semiconductor devices, in fact makes an excellent gate dielectric material in OFETs after suitable purification. Robust ultra-thin films with high glass transition temperature and high dielectric breakdown strength can be obtained by simple spin-coating followed by rapid-thermal-anneal to above 250°C. With this material, we were able to demonstrate remarkable performance in polymer OFETs and explore several aspects of their physics. In Chapter 2, we introduce the use of BCB as a good candidate for solution-processable organic gate dielectric. Pinhole-free ultra-thin gate dielectric film as thin as 50nm can be made from this material. With this gate dielectric, robust continual cyclic operation of poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(phenylene-(N-(p-2-butylphenyl-imino-phenylene)) (TFB) FETs at 120°C was achieved. Previously, the thinnest practical solution-processable gate dielectric thickness was >300 nm-thick. In Chapter 3, we demonstrated self-organised polymer semiconductor/dielectric FETs fabricated using a spontaneous and an unusual vertical phase separation of the TFB polymer semiconductor and the BCB dielectric materials during film spinning. This method enables the formation of semiconductor and dielectric layers at the same time without exposing their interface to air. Using these devices, we established that a critical root-mean-square interface roughness of 0.7 nm (measured on the 100 nm length scale) could be tolerated without loss of mobility of the devices, probably related to the hopping of the carries at the interface. In Chapter 4, we demonstrated using this non-trapping BCB dielectric the generality of n-type field-effect conduction across a wide range of polymer organic semiconductors. We showed that this was previously suppressed by interface trapping of the accumulated electrons by the –OH group in the gate dielectrics that have often been used. We found electron mobilities very similar to, if not larger than, hole mobilities across a range of organic semiconductors. Therefore, many (though not all) π-conjugated materials are by their nature ambipolar and can support both electron and hole conduction nearly equally well. Their previous classification into “n-type” and “p-type” materials is thus somewhat arbitrary. Finally, in Chapter 5, we used BCB as the top gate dielectric and fabricated fully functional double-gate OFETs over a bottom gate dielectric. We showed that such devices exhibit electrostatic coupling of the two gates occurs to produce an “AND” logic gate.
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Leydecker, Tim. "Multiresponsive and supramolecular field-effect transistors." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF056/document.
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Cette thèse a exploré comment, en mélangeant des matériaux avec des propriétés électriques différentes, il est possible de fabriquer des transistors avec des performances accrues. Des transistors organiques à effet de champ basés sur un oligothiophène (DH4T) ont été fabriqués et optimisés jusqu’à ce que les mobilités mesurées fussent supérieures à celles observées dans des films évaporés. Ces résultats ont été obtenus par le contrôle précis des interfaces et de la vitesse d’évaporation. Des polymères de type p ont été mélangés à des polymères de type n. Chaque solution obtenue a été utilisée pour la fabrication de transistors ambipolaires. Les transistors ont été caractérisés et il a été possible de fabriquer des transistors avec des mobilités équilibrées pour chaque paire de polymères. Des transistors à effet de champ basés sur un mélange de P3HT et d’une molécule photochromique (DAE-Me) ont été fabriqués. Le courant a été mesuré pendant et entre les irradiations et il a été démontré qu’une mémoire non-volatile à multiple niveaux peut être fabriquéeThis thesis explored how, by blending of materials with different electrical characteristics, it is possible to fabricate transistors with new or improved performances. First, organic field-effect transistors based on a single oligothiophene, DH4T, were fabricated and optimized until the measured mobility was superior to that observed in vacuum deposited films. This was achieved through careful tuning of the interfaces using self-assembled monolayers and by strong control of the solvent- evaporation rate. P-type polymers were blended with an n-type polymer. Each resulting solution was used for the fabrication of ambipolar field-effect transistors. These devices were characterized and it was found that for each pair of p- and n-type polymers, a transistor with balanced mobilities and high Ion/Ioff could be fabricated. Finally field-effect transistors based on a blend of P3HT and a photoswitchable diarylethene (DAE-Me) were fabricated. The current was measured during and between irradiations and it was demonstrated that a non-volatile multilevel memory could be fabricated
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Nasrallah, Iyad. "Investigating charge trapping effects in organic field-effect transistors." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709425.
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Johnson, Simon. "Field effect transistor type sensors." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259174.
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Robins, Ian. "Gas sensitive field effect transistors." Thesis, King's College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318466.
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Günther, Alrun Aline. "Vertical Organic Field-Effect Transistors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-207731.
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Diese Arbeit stellt eine eingehende Studie des sogenannten Vertikalen Organischen Feld-Effekt-Transistors (VOFET) dar, einer neuen Transistor-Geometrie, welche dem stetig wachsenden Bereich der organischen Elektronik entspringt. Dieses neuartige Bauteil hat bereits bewiesen, dass es in der Lage ist, eine der fundamentalen Einschränkungen herkömmlicher organischer Feld-Effekt-Transistoren (OFETs) zu überwinden: Die für Schaltfrequenz und An-Strom wichtige Kanallänge des Transistors kann im VOFET stark reduziert werden, ohne dass teure und komplexe Strukturierungsmethoden genutzt werden müssen. Das genaue Funktionsprinzip des VOFET ist bisher jedoch weitgehend unerforscht. Durch den Vergleich von experimentellen Daten mit Simulationsdaten des erwarteten Bauteil-Verhaltens wird hier ein erstes, grundlegendes Verständnis des VOFETs erarbeitet. Die so gewonnenen Erkenntnisse werden im Folgenden genutzt, um bestimmte Parameter des VOFETs kontrolliert zu manipulieren. So wird beispielsweise gezeigt, dass die Morphologie des organischen Halbleiters, und damit seine Abscheidungsparameter, sowohl für die VOFET-Herstellung als auch für den Ladungsträgertransport im fertigen Bauteil eine wichtige Rolle spielen. Weiterhin wird gezeigt, dass der VOFET, genau wie der konventionelle OFET, durch das Einbringen von Kontaktdotierung deutlich verbessert werden kann. Mit Hilfe dieser Ergebnisse kann gezeigt werden, dass das Funktionsprinzip des VOFETs mit dem eines konventionellen OFETs nahezu identisch ist, wenn man von geringen Abweichungen aufgrund der unterschiedlichen Geometrien absieht. Basierend auf dieser Erkenntnis wird schließlich ein VOFET präsentiert, welcher im Inversionsmodus betrieben werden kann und so die Lücke zur konventionellen MOSFET-Technologie schließt. Dieser Inversions-VOFET stellt folglich einen vielversprechenden Ansatz für leistungsfähige organische Transistoren dar, welche als Grundbausteine für komplexe Elektronikanwendungen auf flexiblen Substraten genutzt werden könnenThis work represents a comprehensive study of the so-called vertical organic field-effect transistor (VOFET), a novel transistor geometry originating from the fast-growing field of organic electronics. This device has already demonstrated its potential to overcome one of the fundamental limitations met in conventional organic transistor architectures (OFETs): In the VOFET, it is possible to reduce the channel length and thus increase On-state current and switching frequency without using expensive and complex structuring methods. Yet the VOFET's operational principles are presently not understood in full detail. By simulating the expected device behaviour and correlating it with experimental findings, a basic understanding of the charge transport in VOFETs is established and this knowledge is subsequently applied in order to manipulate certain parameters and materials in the VOFET. In particular, it is found that the morphology, and thus the deposition parameters, of the organic semiconductor play an important role, both for a successful VOFET fabrication and for the charge transport in the finished device. Furthermore, it is shown that VOFETs, just like their conventional counterparts, are greatly improved by the application of contact doping. This result, in turn, is used to demonstrate that the VOFET essentially works in almost exactly the same way as a conventional OFET, with only minor changes due to the altered contact arrangement. Working from this realisation, a vertical organic transistor is developed which operates in the inversion regime, thus closing the gap to conventional MOSFET technology and providing a truly promising candidate for high-performance organic transistors as the building blocks for advanced, flexible electronics applications
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Sondell, Niklas. "The wind field in coastal areas." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302884.
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The land-sea transition in coastal areas makes the meteorological conditions rather complex and the structure of the coastal boundary layer is important for many reasons. Two examples are air pollution dispersion and wind energy potential. The wind field off the coast when offshore flow is present has been studied. At the coast there is a sudden change in surface properties that will affect the wind field in the area. When warm air is advected out over the much colder sea we get a stable stratification whose structure depends on wind speed and temperature difference. The roughness length over the sea is much less than over land, which gives less friction over the sea and usually increased winds. This is the general situation. But with a stable stratification the wind speed decreases near the surface partly due to the much denser air. However, there may be a wind speed decrease a certain distance from the coast, after an initial wind speed maximum. This is due to the growth of a stable internal boundary layer that develops over the sea. What is new in this investigation is that the more stable the stratification over the sea is, the farther offshore the decrease in wind speed occurs, probably more than 30 km. Thus with a very stable stratification the wind speed off the coast in coastal areas seems to be increased instead of decreased. This investigation also includes an explanation of why this behavior seldom is seen in measurements. The wind field structure dependence of the IBL-height and the stability has been studied and an expression for the distance to the decrease in wind speed has been found. Also the prediction of a sea breeze circulation is studied as well as the affect a low-level jet has on the wind field near the coast. Measurements from three sites are used, the Baltic Sea near the Island of Gotland, around the strait of Öresund and outside the Atlantic coast near Duck in North Carolina, USA. These measurements are used in simulations with a 2-dimensional meso-γ-scale model as well as a lot of arbitrary simulations. All simulations correspond very well to the expression found and the simulated cases agree well with the measured ones. In the lowest 100 m of the marine atmosphere over the Baltic Sea, the stratification is probably stable more than half of the year. Thus the behavior of decreased wind speeds a certain distance offshore, after an initial increase, would be a very common phenomenon. It must be of great importance in extracting wind energy, to avoid these areas and layers with decreasing wind speed, which in turn have lower wind energy potential. In an area with often very stable stratification over the sea there can be an energy loss of more than 50 % in the lowest 50 m of the boundary layer.Sammanfattning av ”Vindfältet i kustnära områden” Övergången mellan land och hav gör de meteorologiska förhållandena i kustnära områden komplicerade. Vetskap om egenskaperna hos gränsskiktet vid kusten är viktigt av flera orsaker. Några exempel är spridning av luftföroreningar, vindenergipotential samt det faktum att man ska kunna ge rätt vindprognos till dem som av nytta eller nöje befinner sig utanför kusten. Vindfältet utanför kusten vid frånlandsvind har studerats här. Vid kusten sker en plötslig ändring av ytans egenskaper. När varm luft strömmar ut över kallt hav fås en stabil skiktning som beror på vindhastighet och temperaturdifferensen mellan land och hav. Skrovlighetslängden är större över land än över hav. Det ger vanligtvis en ökning av vindhastigheten över havet då luften strömmar från land till hav. Men vid tillräckligt stabil skiktning över hav samt med instabil skiktning över land fås istället ett vindavtagande. Initialt ökar dock alltid vindhastigheten. Det beror på tillväxten av ett internt gränsskikt. Höjden på detta måste vara tillräcklig för att ett avtagande skall ske. Stabilare skiktning över hav ger längre sträcka till avtagandet i vindhastighet som kan ske mer än 30 km utanför kusten och det kan inte längre kallas för kustnära område. Varför detta beteende sällan upptäcks utreds också. Vindfältets beroende av interna gränsskiktets höjd samt stabiliteten har studerats och ett uttryck för att beräkna avståndet till avtagandet i vindhastighet har också tagits fram. Även möjligheten att förutspå en sjöbris har studerats liksom den effekt en low-level jet har på vindfältet nära kusten. Mätningar från tre platser används, Östersjön nära Gotland, över Öresund samt vid Atlantkusten nära Duck i North Carolina, USA. Dessa tre fall simuleras i en 2-dimensionell modell liksom en mängd godtyckliga simuleringar av olika fall. I de lägsta 100 metrarna av det marina gränsskiktet över Östersjön är skiktningen troligen stabil mer än halva året. Beteendet med initialt ökande vindhastighet följt av en dramatiskt avtagande en viss sträcka utanför kusten borde vara ett vanligt fenomen. Vid utvinning av vindenergi måste det vara av stort intresse att undvika dessa områden med lägre vindhastighet, som i sin tur har lägre vindenergipotential. I ett område där det ofta blir stabilt skiktat över havet kan energiförlusten bli på över 50 % i de lägsta 50 metrarna av gränsskiktet.
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Nedic, Stanko. "Zinc oxide nanowire field effect transistors." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708233.
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Lord, Joseph Louis Martin. "FET upconverter design using load dependent mixing transconductance." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28499.
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The conversion gain of GaAs MESFET mixers is known to be dependent on the impedances seen by the applied signals and the resulting mixing products at all ports of the device. For an accurate representation, all these loading conditions should be considered;
however, the design of gate and drain networks then becomes rather difficult. As a result, no sufficiently accurate and yet usable design procedures exist for MESFET mixers; instead, a few simple rules involving short- and open-circuit terminations have been given by various authors. Unfortunately, these rules are often inappropriate, particularly
in upconverter applications.
In this thesis, the conversion efficiency dependence on the drain loading at the local oscillator frequency has been studied for a gate upconverter; the local oscillator signal is by far the most dominant in terms of its influence on mixer performance. It has been found that the conversion gain can significantly deteriorate for a narrow range of load values. In addition, the local oscillator drain termination resulting in highest gain has been found to be generally different from the short-circuit recommended in the literature.
Based on these findings, a novel FET upconverter design procedure has been developed that incorporates the local oscillator loading phenomenon in the FET equivalent circuit by means of a load dependent mixing transconductance. It allows the optimization of the drain network for an acceptable match at the selected sideband and desired local oscillator rejection while avoiding impedance values in the local oscillator frequency range which would otherwise cause severe degradation in conversion gain.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Bégon-Lours, Laura. "Ferroelectric field-effects in high-tc superconducting devices." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066007/document.
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Les supraconducteurs à haute température critique (HTS) sont des systèmes fortement corrélés. Dans ces matériaux, une petite modification du nombre de porteurs peut avoir de grandes conséquences sur leurs propriétés physiques. C'est le cas lorsqu'un matériau ferroélectrique est à proximité immédiate d'un HTS : de manière locale et rémanente, la polarisation ferroélectrique modifie par effet de champ électrostatique le nombre d'électrons dans le HTS, au voisinage de l'interface avec le ferroélectrique. Cet effet peut être exploité dans le but de définir des structures à géométrie variable : dans un premier cas, des jonctions qui consistent en deux électrodes supraconductrices, séparées par une zone où la supraconductivité a été affaiblie par effet de champ. Dans un second cas, des jonctions tunnel ferroélectriques - à nouveau avec des électrodes supraconductrices - où l'épaisseur de la barrière est modulable par effet de champ ferroélectrique. Les travaux menés au cours de cette thèse visent à développer les matériaux et les technologies de lithographie pour fabriquer de telles structures, et à caractériser les propriétés de transport de ces dernièresIn this experimental thesis, we fabricated ferroelectric field-effect devices based on high-Tc superconductors. We grew high-quality epitaxial heterostructures consisting of an ultra-thin (2 to 6 unit cells) film of YBCO and a thin ferroelectric film (BFO-Mn). We fabricated transport measurement microbridges and used a CT-AFM tip to polarise the BFO-Mn outwards or towards the BFO-Mn/YBCO interface. Due to the ferroelectric field-effect, the superconducting properties of the underlying YBCO film were consequently modified. We then used this effect locally in order to design weak links within the microbridges: two regions where the superconducting properties are enhanced are separated by a narrow region where they are depressed. We explored the conditions of existence of a Josephson coupling across this weak link. In parallel, we fabricated ferroelectric junctions. The barrier is an ultra-thin BFO-Mn film sandwiched between a high-Tc superconducting YBCO bottom electrode and a low-Tc superconducting top electrode. Both at room temperature and at low temperature, we characterised the transport properties across the barrier and the resistive switching resulting from the polarisation of the ferroelectric barrier
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Hsu, Fang-Chi. "Electric field effect in "metallic" polymers." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127229727.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxi, 177 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-177). Available online via OhioLINK's ETD Center
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Dvorak, Martin W. "InAs/AlSb heterostructure field-effect transistors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24125.pdf.
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McLaughlin, N. Sheldon J. "InGaP/InGaAs Heterostructure Field Effect Transistors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0028/MQ51414.pdf.
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Mohammad, Ahmed Fareed. "Polyelectrolyte based organic field effect transistors." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96237.
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In this thesis work, the fabrication of dual gate organic field-effect transistors (DGOFETs) using polyanionic proton conductor named polyvinylphosphonic acid and acrylic acid P(VPA-AA), SiO 2 as gate insulating materials and poly(3-hexylthiophene) (P3HT) as organic semiconductor have been studied. Upon operation, the top insulating layer forms large electric double layer capacitors (EDLCs)at the Ti/P(VPA-AA) and P(VPAAA)/ P3HT interfaces. This new type of robust transistor, called as EDLC-OFET, displays fast response (<0.3 ms), a reasonably high field effect mobility (0.0030 cm² V -1 s-1), a low ION/IOFF ratio (150), and operates at low voltage (<1 V). Results concerning the influence of bottom gate on the DG-OFET are presented and discussed. The results presented are important for low-cost printed polymer electronics. Also, various conducting polymer gate electrode in addition to laminated OFET to form EDLC-OFET have been tested. Conducting polymers include PEDOT:PSS and polyaniline (PANI).
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Ritjareonwattu, Supachai. "Ion sensitive organic field effect transistors." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/3292/.
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Ion sensitive organic field-effect transistors (ISOFETs) with a metal–oxide–semiconductor field-effect transistor (MOSFET) architecture have been fabricated by using poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate) (PMMA) as the semiconductor and dielectric layers, respectively. To avoid any pin-holes in the dielectric layer, the ISOFET was coated by two separate PMMA layers. An Ag/AgCl double-junction reference electrode was used as the gate. The results show that the uncoated ISOFET exhibited transistor behaviour in aqueous solutions. However, these devices possessed a small sensitivity of about 0.5 nA dec-1 to H+, K+ and Na+ ions. Langmuir-Blodgett membranes were then used to improve the ISOFET response to the target ions in solution. By coating the gate dielectric (PMMA) with an LB membrane of pure arachidic acid (AA), the ISOFETs showed a significantly higher sensitivity to H+ ions of about 3.5 nA pH-1, but no improvement in the pK response (< 0.5 nA dec-1). The compact ionised layers of carboxylic acid head groups were thought to lead to the improvement in the pH sensitivity; however, the layers of long hydrocarbon chains prevented large monovalent ions, such as K+ and Na+, from interacting with the ionised carboxylic acid head groups. ISOFETs coated with an arachidic acid/valinomycin (AA/val) mixture did not show any selectivity to K+ ions, but exhibited enhanced sensitivities to both K+ and Na+ ions. Instead of trapping K+ ions, the valinomycin molecules in the AA membrane were thought to disrupt the membrane architecture and provide ion-leakage channels. Pure valinomycin-coated ISOFETs also revealed enhancements in both sensitivity and selectivity to K+ ions over Na+. This may be due to the fact that the cavity in the valinomycin molecules can accommodate a K+ ion but not a Na+ ion. To study facilitated K+ transport across the membrane, LB films of AA/val mixture and pure valinomycin were coated on porous supports. The responses of both uncoated and coated membranes were similar. After deposition, collapse of the LB film into the pores may provide leakage channels. This probably led to the observed gradual decrease of the potentials across the membranes.
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Opoku, Charles. "Solution processable nanowire field-effect transistors." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580355.
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The use of orientated semiconducting nanowires as the active material in solution processable printable transistors is an area of research that can offer enormous potential in the field of high performance electronics. Lightweight, flexible and low cost components that are compatible with plastic substrates can further increase the appeal of this field. Currently, the most commonly used materials for field-effect transistors in large area electronics are polycrystalline, amorphous silicon and organic semiconductors. However, these classes of semiconductors face several limitations with regards to their compatibility in plastic electronics, either due to their high temperature processing (silicon) or low charge carrier mobility (organics). The current work investigates alternative semiconductors based on nanomaterials that can be used as active layers in large area electronics, with performances comparable to or exceeding those of amorphous silicon which can be processed at much lower temperatures. In this thesis, we explore semiconducting inorganic nanowires including silicon, germanium, and zinc oxide nanowires as the channel material in field-effect transistors to realise high performance printed electronics. Several main challenges, such as deposition of nanowire 'inks', ohmic contacts to nanowires, surface states, and the use of organic dielectrics are addressed as follows: (1) Development of two new nanowire deposition methods based on either spray coating or dip-coating has led to alignment control for nanowires and also high density coatings on various substrates. These techniques can offer scalability for large area surfaces at room temperature. (2) Solving problems of making near-ohmic contacts m nanowire transistors fabricated at low temperatures ensured efficient charge injection m devices. Optimised FETs with high work function metal electrodes and treated nanowire surfaces exhibited high output currents reaching 1mA, high on/off current modulation of ~ 107, and high hole mobility in the range of 5-26cm2Ns. (3) Investigation of high Schottky barrier nanowire FETs led to better understanding of source contact barrier lowering by the gate field and the discovery of a new type of nanowire transistor operation that can offer improved power dissipation and near ideal current-voltage saturation. characteristics with drain voltage saturation of less than 2V, even at large gate voltages. (4) The control of nanowire surfaces, especially at the nanowire-insulator interface was achieved using low-k organic dielectrics and self-assembled monolayers. This also resulted in the demonstration of high performance p-type transistors exhibiting 10uA output current, on/off current ratio of ~107 and the high field-effect mobility in the range of 5-20cm2/V-s. (5) Finally, a high performance n-type ZnO nanowire transistor on a flexible plastic substrate with a low-k dielectric was demonstrated with output current of ~1uA, on/off current modulation of ~105, subthreshold voltage swing of ~O.26mV/dec and a field-effect mobility in the range of 49- 65cm2/V-s. In short, this thesis delivers a new realisation of a concept in which solution processable high performance electronic devices may be fabricated using low temperature processing steps on various substrates including plastics. The approach is general to a broad range of nanowire material systems and can be applied to e-paper, flexible displays, chemical and biological sensors, RFID tags, memory elements and ambient intelligence devices.
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Lowe, Benjamin Mark. "Interfacial physics of field-effect biosensors." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/419586/.
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Field-Effect Transistor-sensors (FET-sensors) are a class of pH and biomolecule sensors that can be produced at a low cost and with high sensitivity, as a result having potential for commercialisation and widespread use. The response of a FET-sensor is generated when the electric field at the sensor surface changes, thereby inducing a measurable change in current through the device. The electric field can be modified by pH or by binding of an analyte to the surface. The solid state counterpart, the Metal Oxide Semiconductor FET, has been extensively studied as it is the basis of modern electronics. FET-sensors are less well understood, mainly due to the inherent complexity introduced by the aqueous media present at the sensor surface. The FET-sensor surface is usually an oxide such as silica and its interaction with aqueous solution introduces many complex effects, such as ion-dynamics and pH dependent ionisation, which make these systems non-trivial to understand and predict. To-date, most models of FET-sensor response have relied upon mean-field assumptions which neglect the multi-scale nature of the system and even qualitative predictions of FET-sensor response remain challenging. In the work presented here, the interfacial physics of FET-sensors were modelled using a variety of simulation techniques at different time- and length-scales. Acid-base surface charging reactions at the oxide surface of the sensor are an important part of FET-sensor response. Density Functional Theory (DFT) simulations revealed a new mechanism of surface charging and also showed that these reactions have no well-defined transition state which can be used to model their kinetics. A Kinetic Monte Carlo (KMC) model was validated that can be used describe the dynamics of surface-charging reactions on a device scale. As FET-sensors operate by detecting changes in the interfacial electric field, the mean net charge density of surface-bound biomolecules is an important parameter in most models of BioFET response. Semi-empirical calculations were performed to estimate the net charge of two different biomolecular systems relevant to biosensing studies. The ion dynamics in the electrical double layer at the silicawater-biomolecule interface were investigated using classical Molecular Dynamics (MD) simulations, which suggested that, in contrast to commonly used net-charge arguments for FET-sensor response, the importance of water polarisation for FET-sensor response has been hitherto underestimated. A quantitative analysis of data extracted from the FET-sensor literature was performed, comparing experimental biosensing data with pH-sensing data. This revealed some frequent problems related to reproducibility and comparability of experimental data in this field, and highlighted that optimisation of surface chemistry is an underappreciated component of sensor optimisation. Despite these limitations, BioFET research is a rapidly advancing field in which novel device design and operation methodologies are constantly being developed which increase the viability of BioFET devices for commercial use.
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Liu, Shiyi. "Understanding Doped Organic Field-Effect Transistors." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574127009556301.
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Wiederspahn, H. Lee. "Quantum model of the modulation doped field effect transistor." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13355.
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Wasapinyokul, Kamol. "Effects of illumination on the properties of organic field-effect transistors." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609509.
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Gwinner, Michael Christian. "High-performance light-emitting polymer field-effect transistors." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610236.
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GALANTI, FRANCESCO. "Electric field effect in disordered thin films." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2823944.
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Rubino, Edoardo. "Magnetic field and electric field effect on magnetostrictive and electrostrictive photonic resonators." Thesis, Southern Methodist University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10247565.
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The goal of this work is to investigate the effect of electric and magnetic field on the optical resonances of electrostrictive and magnetorheological optical resonators. The optical resonances, also known as whispering gallery modes (WGM) or morphology dependent resonances (MDR) experience a shift in the transmission spectrum whenever the resonator changes its size and/or index of refraction. Their small size, the elimination of electrical cabling, and the high optical quality factor, Q, make them attractive for a large number of applications. In these studies, we investigate the magnetostrictive and the electrostrictive effect of fiber coupled photonic spherical resonators. The electrostrictive and the magnetostrictive effect are the elastic deformation of a solid when subject to an electric or magnetic field respectively. In these studies, three different configurations were investigated to tune the optical modes of the spherical optical resonator. In the first configuration, the resonator was fabricated by embedding magnetic micro particles in a polymeric matrix of PVC plastisol (commercial name super soft plastic, SSP). For these configurations we studied the WGM shift that was induced when the sphere was immersed in a static and a harmonic magnetic field. These results lead to the development of a magnetic flied sensor and a non-contact transduction mechanism for displacement measurements. The sphere showed a sensitivity to the magnetic field of 0.285 pm/mT and to the displacement of 0.402 pm/?m. These values lead to a resolution of 350 ?T and 248 nm respectively. The second configuration was a microsphere that was made of pure super soft plastic and was subject to a static and harmonic electric field. The results lead to the development of a non-contact displacement sensor whose sensitivity is 0.642 pm/?m and the resolution is 155 nm. Both studies also indicate for the first time that it is possible to couple light into a PVC compound and achieve high optical quality factor of the order of 106. The third configuration was a metglas film that was mechanically coupled to a PDMS microsphere. The results of these studies lead to the development of a magnetic field sensor with sensitivity and resolution of 0.6 pm/?T and 166 nT respectively. In conclusion, these studies lead to a fundamental understanding of the dynamical behavior of electrostrictive and magnetorheological optical resonators and its potential for sensing applications. In addition, these devices could be embedded into polymeric matrix for the development of materials with actuation and sensing capabilities.
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Zhang, Xiaohong. "Device engineering of organic field-effect transistors toward complementary circuits." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28150.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Kippelen, Bernard; Committee Member: Brand, Oliver; Committee Member: Graham, Samuel; Committee Member: Rohatgi, Ajeet; Committee Member: Shen, Shyh-Chiang.
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Wehrfritz, Peter, and Thomas Seyller. "The Hall coefficient: a tool for characterizing graphene field effect transistors." Technische Universität Chemnitz, 2014. https://monarch.qucosa.de/id/qucosa%3A21189.
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Graphene field effect transistors (GFETs) are considered as a candidate for future high-frequency applications. For their realization, the optimal combination of substrate, graphene preparation, and insulator deposition and composition is required.This optimization must be based on an in-depth characterization of the obtained graphene insulator metal (GIM) stack. Hall effect measurements are frequently employed to study such systems, thereby focussing primarily on the charge carrier mobility. In this work we show how an analysis of the sheet Hall coefficient can reveal further important properties of the GIM stack, like, e.g., the interface trap density and the spacial charge inhomogeneity. To that end, we provide an extensive description of the GIM diode, which leads to an accurate calculation of the sheet Hall coefficient dependent on temperature and gate voltage. The gate dependent inverse sheet Hall coefficient is discussed in detail before we introduce the concept of an equivalent temperature, which is a measure of the spacial charge inhomogeneity. In order to test the concept, we apply it to evaluate already measured Hall data taken from the literature. This evaluation allows us to determine the Drude mobility, even at the charge neutrality point, which is inaccessible with a simple one band Hall mobility analysis, and to shed light on the spacial charge inhomogeneity. The formalism is easily adaptable and provides experimentalists a powerful tool for the characterization of their graphene field effect devices.
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Chen, Si. "Electronic Sensors Based on Nanostructured Field-Effect Devices." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-194015.
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Point-of-care (POC) diagnostics presents a giant market opportunity with profound societal impact. In particular, specific detection of DNA and protein markers can be essential for early diagnosis of e.g. cancer, cardiovascular disease, infections or allergies. Today, identification of these markers often requires extensive laboratory work and hence is expensive and time consuming. Current methods for recognition and detection of specific biomolecules are mostly optics based and thus impose severe limitations as to convenience, specificity, sensitivity, parallel processing and cost reduction. Electronic sensors based on silicon nanowire field-effect transistors have been reported to be able to detect biomolecules with concentrations down to femtomolar (fM) level with high specificity. Although the reported capability needs further confirmation, the CMOS-compatible fabrication process of such sensors allows for low cost production and high density integration, which are favorable for POC applications. This thesis mainly focuses on the development of a multiplex detection platform based on silicon nanowire field-effect sensors integrated with a microfluidic system for liquid sample delivery. Extensive work was dedicated to developing a top-down fabrication process of the sensors as well as an effective passivation scheme. The operation mechanism and coupling efficiencies of different gate configurations were studied experimentally with the assistance of numerical simulation and equivalent circuits. Using pH sensing as a model system, large effort was devoted to identifying sources for false responses resulting from the instability of the inert-metal gate electrode. In addition, the drift mechanism of the sensor operating in electrolyte was addressed and a calibration model was proposed. Furthermore, protein detection experiments were performed using small-sized Affibody molecules as receptors on the gate insulator to tackle the Debye screening issue. Preliminary results showed that the directionality of the current changes in the sensors was in good agreement with the charge polarities of the proteins. Finally, a graphene-based capacitor was examined as an alternative to the nanowire device for field-effect ion sensing. Our initial attempts showed some attractive features of the capacitor sensor.
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Grecu, Silviu-Cosmin. "Charge transport in polymeric field-effect devices." kostenfrei kostenfrei, 2008. http://d-nb.info/996047514/34.
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Frenzel, Heiko. "ZnO-based metal-semiconductor field-effect transistors." Doctoral thesis, Universitätsbibliothek Leipzig, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-61957.
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Die vorliegende Arbeit befasst sich mit der Entwicklung, Herstellung und Untersuchung von ZnO-basierten Feldeffekttransistoren (FET). Dabei werden im ersten Teil Eigenschaften von ein- und mehrschichtigen Isolatoren mit hohen Dielektrizitätskonstanten betrachtet, die mittels gepulster Laserabscheidung (PLD) dargestellt wurden. Die elektrischen und kapazitiven Eigenschaften dieser Isolatoren innerhalb von Metall-Isolator-Metall (MIM) bzw. Metall-Isolator-Halbleiter (MIS) Übergängen wurden untersucht. Letzterer wurde schließlich als Gate-Struktur in Metall-Isolator-Halbleiter-FET (MISFET) mit unten (backgate) bzw. oben liegendem Gate (topgate) genutzt. Der zweite Teil konzentriert sich auf Metal-Halbleiter-FET (MESFET), die einen Schottky-Kontakt alsGate nutzen. Dieser wurde mittels reaktiver Kathodenzerstäubung (Sputtern) von Ag, Pt, Pd oder
Au unter Einflußvon Sauerstoff hergestellt. ZnO-MESFET stellen eine vielversprechende Alternative zu den bisher in der Oxid-basierten Elektronik verwendeten MISFET dar. Durch die Variation des
verwendeten Gate-Metalls, Dotierung, Dicke und Struktur des Kanals und Kontakstruktur, wurde ein Herstellungsstandard gefunden, der zu weiteren Untersuchungen herangezogen wurde. So wurde die
Degradation der MESFET unter Belastung durch dauerhaft angelegte Spannung, Einfluss von Licht und erhöhten Temperaturen sowie lange Lagerung getestet. Weiterhin wurden ZnO-MESFET auf industriell
genutztem Glasssubstrat hergestellt und untersucht, um die Möglichkeit einer großflächigen Anwendung in Anzeigeelementen aufzuzeigen. Einfache integrierte Schaltungen, wie Inverter und
ein NOR-Gatter, wurden realisiert. Dazu wurden Inverter mit sogenannten Pegelschiebern verwendet, welche die Ausgangsspannung des Inverters so verschieben, dass eine logische Aneinanderreihungvon Invertern möglich wird. Schließlich wurden volltransparente MESFET und Inverter, basierend auf neuartigen transparenten gleichrichtenden Kontakten demonstriert.
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Fouts, John Lyle. "Forming Screen Effect on Ultrasonic Beam Field." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10423.
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The aim of this study was to characterize the interaction between a pulsed ultrasonic wave and a paper forming screen for potential development of a smart paper forming sensor to measure velocity profile of the forming jet as it impinges on the wire. To achieve this goal, a Signal-Processing DOP 2000 pulsed ultrasonic Doppler velocimeter was used to generate a pulsed ultrasonic signal. The signal was transmitted and received using four different ultrasonic transducers: a 2 MHz 10 mm, 4 MHz 5 mm, 4MHz 8 mm focused, and 8 MHz 5 mm. The ultrasonic signals were then analyzed in order to determine the ultrasonic beam echo amplitude and shape. These tests were performed with and without various paper forming screens placed between the ultrasonic transducer and an ultrasonic signal target.
Two different paper forming screens were utilized to study the interaction of the ultrasonic beam with the forming screens. The tests showed that the ultrasonic signal passing through the forming screens is greatly attenuated causing a sharp decrease in echo amplitude. To overcome the attenuation of the signal, a much higher amplification of the signal was used causing an increase in the saturation region around the forming screen. This increased the minimum distance that a target had to be away from the forming screen. The closest distance from the plastic sphere to the screen over the widest range of transducer-screen-distances that produced detectable echoes was achieved with the 4 MHz 5 mm transducer. The tests showed for both screens that there is more variation in beam width when the screen is moved laterally than when it is not moved at all. They also show that even though the pores in the forming screen are very small, they seem to have a great effect on the beam width measurements of the ultrasonic transducer.
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Wolanin, Piotr Jacek. "Functional organic nanomaterials for field-effect transistors." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723471.
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Takshi, Arash. "Organic metal-semiconductor field-effect transistor (OMESFET)." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31531.
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Organic electronics offers the possibility of producing ultra-low-cost and large-area electronics using printing methods. Two challenges limiting the utility of printed electronic circuits are the high operating voltage and the relatively poor performance of printed transistors. It is shown that voltages can be reduced by replacing the capacitive gate used in Organic Field-Effect Transistors (OFETs) with a Schottky contact, creating a thin-film Organic Metal-Semiconductor Field-Effect Transistor (OMESFET). This geometry solves the voltage issue, and promises to be useful in situations where low voltage operation is important, but good performance is not essential. In cases where high voltage is acceptable or required, it is shown that OFET performance can be greatly improved by employing a Schottky contact as a second gate. The relatively thick insulating layer between the gate and the semiconductor in OFETs makes it necessary to employ a large change of gate voltage (~40 V) to control the drain current. In order to reduce the voltage to less than 5 V a very thin (<10 nm) insulating layer and/or high-k dielectric materials can be used, but these solutions are not compatible with current printing technology. Simulations and implementations of OMESFET devices demonstrate low voltage operation (<5 V) and improved sub-threshold swing compared to the OFET. However, these benefits are achieved at the expense of mobility. In order to achieve good performance in an OFET, including threshold voltage, current ratio and output resistance, the semiconductor thickness has to be less than 50 nm, whereas the thickness of a printed semiconductor is typically larger than 200 nm. The addition of a top Schottky contact on the OFET creates a depletion region thereby reducing the effective thickness of the semiconductor, and resulting in enhanced transistor performance. Simulations and experimental results show improvements in the threshold voltage, the current ratio, and the output resistance of a dual gate transistor, when compared to those in an OFET of the same thickness. The transistors introduced in this work demonstrate means of improving the performance of thick-film OFETs and of achieving substantially lower operation voltage in organic transistors.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Dölle, Michael. "Field effect transistor based CMOS stress sensors /." Tönning ; Lübeck Marburg : Der Andere Verlag, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016086105&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Cheng, X. "Organic field-effect transistors via inkjet printing." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597572.
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This thesis is concerned with the fabrication process, charge injection, dielectric preparation and downscaling of organic field-effect transistors via inkjet printing. To provide a general guideline of fabricating inkjet-printed short channel transistors, this thesis starts with an improved self-aligned printing (SAP) technique implemented with gold nanoparticle inks which defines a nanometer scale channel between source and drain electrodes. Electron and hole injection and transport in the channel is studied using ambipolar semiconductor F8BT. Contact resistance effects are found to be significantly more pronounced in these short channel devices and the current is limited by insufficient charge injection. Self-assembled monolayers (SAMs) are effectively employed to reduce the contact resistance in the SAP. Next, the systematic control of electron and hole charge injection in top-gate F8BT ambipolar transistor via SAM modification is investigated. Gold electrodes are modified with PFDT and 1DT to reduce contact resistance and improve charge injection. Furthermore, a crosslinked fluoropolymer Cytop (C-Cytop) is adopted as an ultrathin gate dielectric, which is necessary for proper gate control of the accumulation layer in short channel devices. The C-Cytop can be spin-coated in air with uniform thin films, low gate leakage and high dielectric breakdown strength. The yield and stability of C-Cytop devices are remarkable compared to other non-fluorinated polymer dielectrics and less dependent on the underlying semiconductor roughness. In particular high performance in-type transistors are demonstrated using C-Cytop and small-molecule ActivInk N1400 as the semiconductor. Finally, downscaled inkjet-printed nano-channel n-type transistors are demonstrated by printing silver nanoparticle inks with N1400 and C-Cytop in the SAP structure. The printed silver nanoparticles serves as source contact combining with thin C-Cytop layer as gate dielectric.
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Cooper, Emily Barbara 1977. "Silicon field-effect sensors for biomolecular assays." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87450.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references.
System-level understanding of biological processes requires the development of novel biosensors capable of quantitative, real-time readout of molecular interactions. Label-free detection methods can minimize costs in time and resources by obviating preparatory steps necessary with label-based methods. They may further be valuable for monitoring biomolecular systems which are difficult or impossible to tag, or for which reporter molecules interfere with biological function. Field-effect sensing is a method of directly sensing intrinsic electrical charge associated with biomolecules without the need for reporter molecules. Microfabrication of field-effect biosensors enables their integration in compact microanalytical systems, as well as the potential to be scaled down in size and up in number. Applying field-effect sensing to the detection and real-time monitoring of specific molecular interactions has long been of interest for protein and nucleic acids analysis. However, these applications are inhibited by serious practical limitations imposed by charge screening in solution. The development of effective measurement techniques requires inquiry into aspects of device engineering, surface chemistry, and buffer conditions. This thesis describes a body of experimental work that investigates the feasibility of label-free analysis of biomolecular interactions by field-effect. This work begins with the microfabrication of field-effect sensors with extremely thin gate oxide, which enables improved surface potential resolution over previously reported sensors.
(cont.) The performance of these sensors has been characterized in terms of drift, noise, and leakage. To better understand the applicability of these sensors, we have characterized the sensors' response to pH, adsorption of polyelectrolyte multilayers, and high-affinity molecular recognition over a range of buffer conditions. Direct, label-free detection of DNA hybridization was accomplished by combining the high-resolution sensors, with enabling surface chemistry, and a differential readout technique. Finally, we explore the lateral scaling limits of potentiometry by applying a novel nanolithographic technique to the fabrication of a single electron transistor that demonstrates Coulomb oscillations at room temperature.
by Emily Barbara Cooper.
Ph.D.
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Richards, Timothy James. "Internal potentiometry of polymer field effect transistors." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613272.
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Nukala, Prathyusha. "Development of Silicon Nanowire Field Effect Transistors." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc103364/.
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An economically reliable technique for the synthesis of silicon nanowire was developed using silicon chloride as source material. The 30-40 micron long nanowires were found to have diameters ranging from 40 – 100 nm. An amorphous oxide shell covered the nanowires, post-growth. Raman spectroscopy confirmed the composition of the shell to be silicon-dioxide. Photoluminescence measurements of the as-grown nanowires showed green emission, attributed to the presence of the oxide shell. Etching of the oxide shell was found to decrease the intensity of green emission. n-type doping of the silicon nanowires was achieved using antimony as the dopant. The maximum dopant concentration was achieved by post-growth diffusion. Intrinsic nanowire parameters were determined by implementation of the as-grown and antimony doped silicon nanowires in field effect transistor configuration.
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Rodrigues, Frâncio Souza Berti. "Fabrication of ion sensitive field effect transistors." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/183198.
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Transistores de Efeito de Campo Sensíveis a Íons (ISFETs) revolucionaram a tecnologia de sensores químicos e de pH por serem pequenos e compatíveis com tecnologias de microfabricação em grande escala. Nós desenvolvemos uma metodologia para fabricar e caracterizar sensores ISFET para medida de pH no laboratório de microeletrônica da UFRGS. Sensores ISFET do tipo NMOS com camadas de silica e alumina foram fabricados com tecnologa CMOS padrão. Transistores de W=1000 m e L=10 m foram fabricados em conjunto para monitorar o processo de fabricação através de medidas de Capacitância- Tensão (C-V) e Corrente-Tensão (I-V). Os dispositivos foram colados em suportes de circuito impresso, manualmente microsoldados e encapsulados com cola epoxy. Com o dispotivo na ponta, o suporte foi conectado a um Analisador de Parâmetros de Semicondutores em conjunto com um eletrodo de referência comercial de Ag/AgCl e imersos em soluções de pH diferente para a realização de medidas de pH. A sensibilidade à variação de pH, definida como a variação na tensão de limiar devido a presença do eletrólito, para os sensores de silica foi de 30mV/pH em ácidos e 24mV/pH para bases. Sensores de alumina tiveram uma performance muito superior e exibiram sensibilidade de 32mV/pH em ácidos e 48mV/pH em bases. A tecnologia de fabricação e o conhecimento experimental desenvolvidos nesse trabalho fornecem uma fundação essencial para projetos de pesquisa locais que buscam a aplicação de sensores de estado sólido no sensoriamento de sistemas químicos ou biológicos.
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Arthur, Joshua N. "Hygroscopic insulator organic field effect transistor sensors." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232689/1/Joshua_Arthur_Thesis.pdf.
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Hygroscopic insulator field effect transistors (HIFETs) are organic transistors with promising characteristics for biosensing applications. However, their fundamental sensing mechanisms are not yet fully understood. This thesis explores HIFET sensors through detailed electrical and optical characterisation, providing vital insights into the distinct mechanisms by which HIFETs detect biologically relevant chemicals. Hydrogen peroxide, a by-product of enzymatic reactions, oxidises the organic semiconductor, modulating the output current. Ionic solutions, such as KCl, NaCl and HCl, modulate the current by changing double layer capacitance. These insights are foundational for the continued development of HIFETs as effective multipurpose biosensing platforms.
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Vishnoi, Rajat. "Modelling of nanoscale tunnelling field effect transistors." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7030.
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Chen, Hang. "Modulation Effects on Organic Electronics." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7594.
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A high aspect ratio epoxy mask has been built with Taiyo PSR4000BN on chemical sensing array chip. Thickness up to 200 and #61549;m and aspect ratio up to 16:1 have been achieved with this material. It is demonstrated that this material satisfies the mechanical and chemical requirements. A three-electrode system has been designed and built for electrochemistry in micro-cell on chip. Tests with poly(phenylenesulfide-phenyleneamine) (PPSA) demonstrates that it is possible to precisely tune the properties (Work function and resistance) of conducting polymer that has been cast on chip surface.
A new test platform GT03 has been fabricated and used to characterize the chemical effects on organic electronics. It is demonstrated that the chemical species in ambient environment can affect organic electronics properties on bulk, interface and electric contact. The contact resistance in organic field-effect transistors (OFETs) has been characterized with modified interdigitated structure (IDS). It is demonstrated that drain and source contact resistances can be calculated separately with modified four-point-probe measurements, and contact resistance and material bulk resistance are actually modulated by the gate electric field. Furthermore, the influence from oxygen doping in poly(3-hexylthiophene) (P3HT) based OFETs has been investigated. A new model of oxygen doping has been suggested and it is demonstrated that oxygen doping can affect all the resistance components in P3HT OFETs.
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Champion, Corbin Leigh. "Modeling of FETs with abnormal gate geometries for radiation hardening." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Thesis/Summer2004/c%5Fchampion%5F072204.pdf.
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Schmidt, Jörg. "Dual-field-of-view Raman lidar measurements of cloud microphysical properties." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-150408.
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Im Rahmen der vorliegenden Arbeit wurde eine neuartige Lidartechnik in ein leistungsstarkes Lidar-System implementiert. Mit Hilfe des realisierten Aufbaus wurden Aerosol-Wolken-Wechselwirkungen in Flüssigwasserwolken über Leipzig untersucht.
Die angewandte Messmethode beruht auf der Detektion von Licht, das an Wolkentröpfchen mehrfach in Vorwärtsrichtung gestreut und an Stickstoffmolekülen inelastisch zurückgestreut wurde. Dabei werden zwei Gesichtsfelder unterschiedlicher Größe verwendet. Ein Vorwärtsiterations-Algorithmus nutzt die gewonnenen Informationen zur Ermittlung von Profilen wolkenmikrophysikalischer Eigenschaften. Es können der Extinktionskoeffizient, der effektive Tröpfchenradius, der Flüssigwassergehalt sowie die Tröpfchenanzahlkonzentration bestimmt werden. Weiterhin wird die exakte Erfassung der Wolkenunterkantenhöhe durchdie eingesetzte Messtechnik ermöglicht. Darüber hinaus ist die Bestimmung von Aerosoleigenschaften mit dem eingesetzten Lidargerät möglich.
Die Qualität des realisierten Messaufbaus wurde geprüft und eine Fehleranalyse durchgeführt. Unter anderem wurde der aus einer Wolkenmessung bestimmte Flüssigwassergehalt mit einem Mikrowellen-Radiometer bestätigt.
Anhand von Fallbeispielen konnte das Potential dieser Messtechnik demonstriert werden. Die Bedeutung von Profilinformationen von Wolkeneigenschaften für die Untersuchung von Aerosol-Wolken-Wechselwirkungen wurde gezeigt. Weiterhin wurde mit Hilfe eines Doppler-Windlidars der Einfluss der Vertikalwindgeschwindigkeit auf Wolkeneigenschaften und damit Aerosol-Wolken-Wechselwirkungen verdeutlicht.
Neunundzwanzig Wolkenmessungen wurden für eine statistische Auswertung bezüglich Aerosol-Wolken-Wechselwirkungen genutzt. Dabei konnte erstmalig die Abhängigkeit von Aerosol-Wolken-Wechselwirkungen von der Wolkeneindringtiefe untersucht werden. Es wurde festgestellt, dass diese auf die untersten 70m von Wolken beschränkt sind. Weiterhin wurden deutlich stärkere Aerosol-Wolken-Wechselwirkungen in Wolkengebieten festgestellt, die von Aufwinden dominiert werden.
Für der Quantifizierung der Stärke von Aerosol-Wolken-Wechselwirkungen wurden ACIN-Werte genutzt, welche den Zusammenhang zwischen der Tröpfchenanzahlkonzentration und dem Aerosol-Extinktionskoeffizienten beschreiben. Dabei wurde zwischen der Untersuchung der entsprechenden mikrophysikalischen Prozesse und deren Bedeutung für die Wolkenalbedo und damit dem Strahlungsantrieb der Wolken unterschieden. Für die erstgenannte Zielstellung wurde ein ACIN-Wert von 0.80 +/- 0.40 ermittelt, für Letztere 0.13 +/- 0.07.
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Lebby, M. S. "Fabrication and characterisation of the Heterojunction field effect transistor (HFET) and the bipolar inversion channel field effect transistor (BIFCET)." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379863.
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Shi, Xuejie. "Compact modeling of double-gate metal-oxide-semiconductor field-effect transistor /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202006%20SHI.
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He, Xing-Hong. "Non-hydrogenic systems in a magnetic field." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337037.
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He, Ruicong, and 何锐聪. "Photocurrent study on bulk and few layers MoS₂ field effect transistors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/212610.
Full textAbstract:
Atomically thin Molybdenum disulfide, MoS2, a star member of the group VI transition metal dichalcogenide(TMDC) family has been attracting rising interests for its potential applications in emerging electronics and optoelectronics. Bulk MoS2is a semiconductor with an indirect gap located between the top of valence band at Γ points and the bottom of conduction band in mid of K and Γ points in its Brillouin zone. Atomically thin MoS2 films including monolayers and multilayers, being chemically inert, present a class of intrinsic 2D semiconductors which are widely regarded as a platform for ultimate electronics.
As yet tremendous efforts focus on the optical properties and electric transport study. In this thesis, we report the experimental study of photocurrent measurements on MoS2thin films. The sample preparation, device fabrication, optical and electric characterizations are introduced. The experiments have been carried out on a field effect transistor (FET) structured MoS2 device. The photocurrent spectroscopy reveals the interband excitonic transitions at spin-split bands around K valleys. The results demonstrate that MoS2has potential applications in optoelectronics.published_or_final_version
Physics
Master
Master of Philosophy
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Vega, Reinaldo A. "Schottky field effect transistors and Schottky CMOS circuitry /." Online version of thesis, 2006. http://hdl.handle.net/1850/5179.
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