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Sensors based on carbon nanotube field-effect transistors and molecular recognition approachesCid Salavert, Cristina Carlota 23 January 2009 (has links)
La unión de las propiedades de los CNT con los principios de reconocimiento molecular se presenta como una base adecuada para el desarrollo de sensores altamente específicos. El objetivo de la presente tesis ha sido desarrollar sensores químicos, del tipo transistores de efecto campo (CNTFET), basados en interacciones receptor-analito, mediante el empleo de los nanotubos de pared sencilla (SWCNT), que actúan como transductores de la señal analítica.Las principales etapas de la parte experimental han sido: Crecimiento de SWCNT con la técnica de deposición química en fase vapor. Integración de los SWCNTs en sistemas CNTFET. Empleo del CNTFET como base del sensor en distintos campos utilizando modelos de reconocimiento molecular. Dependiendo del tipo de funcionalización de los SWCNTs se pueden obtener sensores para proteínas, iones, etc. Como resultado, se han desarrollado y estudiado sensores basados en CNTFETs para la detección distintos analitos de interés, como son la Inmunoglobulina G Humana, los iones potasio y el dióxido de azufre. / The general objective of this thesis is to develop chemical sensors whose sensing capacities are based on the principle of molecular recognition and where the transduction is carried out by single-walled carbon nanotubes (SWCNT).The sensing device used is the carbon nanotube field-effect transistor (CNTFET). The new structure of the CNTFET allows nanotubes to be integrated at the surface of the devices, thus exploiting SWCNTs' sensitivity to changes in their environment. The functionalization of SWCNTs with several types of molecular receptors such as antibodies, ion selective membranes, and synthetic receptors, achieve a high selectivity towards the analyte of interest. This thesis shows that CNTFETs can be used for the successful selective detection of different types of target analytes. These can be biomolecules such as antigens, small compounds such as cations or gas-phase compounds such as SO2.
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Towards Quantum-limited Measurement with the Radio Frequency Superconducting Single-Electron TransistorPierobon, Scott Carson 17 August 2010 (has links)
In the past decade, nanomechanical resonators have found use in the work towards understanding mesoscopic quantum systems and the necessary validation of quantum mechanics on this scale. In 2010, the observation and state manipulation of a nanomechanical quantum system was achieved for the first time by O'Connell et al.. In 2002, Knobel and Cleland proposed to use a radio frequency superconducting single-electron transistor (RF-SSET), a fast and sensitive charge amplifier, to sense the quantum-limited motion of a piezoelectrically coupled nanomechanical resonator. The work presented in this thesis is towards the realization of the RF-SSET component of this device. An in-house fabrication recipe for making SETs with tunnel junction areas < 100^2 nm^2 and resistances between 20 kΩ and 150 kΩ was developed, in the end producing six SETs with resistances (36 ± 8) kΩ that were not susceptible to aging effects. Three measurement circuits were designed and used to characterize one of these SETs in the superconducting state (SSET) and operated in the DC and RF modes in a cryostat at a base temperature of 320~mK. Lock-in measurements revealed the SSET junction capacitances as 206 and 305 aF, contributing to a charging energy of (296 ± 11) x 10^(-6) eV. The resonant LC tank, which permitted RF operation, was also characterized at base temperature. The charge sensitivity of the RF-SSET was 6.8 x 10^(-5) e/√Hz (with uncertainty between 9.6 x 10^(-4) e/√Hz and 3.5 x 10^(-5) e/√Hz). With moderate improvements to the impedance matching network formed with the LC tank and greater junction resistances, an RF-SSET charge sensitivity on the order of 10^(-6) e/√Hz, required for sensing the quantum-limited motion of the nanomechanical resonator, should be achieved. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-08-10 17:38:43.798
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An Analytic model for high electron mobility transistors.Hill, Adrian John. January 1986 (has links)
The last six years has seen the emergence and rapid development of a new
type of field effect transistor, the High Electron Mobility Transistor
(HEMT), which offers improved performance in both digital and analogue
circuits compared with circuits incorporating either MEtal Semiconductor
(MES) or Metal Oxide Semiconductor (MOS) FETs. A new physically-based
analytic model for HEMTs, which predicts the DC and RF electrical
performance from the material and structural parameters of the device,
is presented. The efficacy of the model is demonstrated with comparisons
between simulated and measured device characteristics, at DC and
microwave frequencies.
The good agreement with experiment obtained with the model indicates
that velocity overshoot effects are considerably less important in HEMTs
than has been widely assumed, and that the electron transit velocity in
submicron devices is approximately 10
cm/s, rather than around 2x10
cm/s.
The Inverted HEMT, one of the major HEMT structural variants, is
emphasized throughout this work because of its potential advantages over
other variants, and practical results from 0.5 micron gate length
Inverted HEMTs are presented. / Thesis (Ph.D.)-University of Natal, Durban, 1986.
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Novel Metallic Field-effect TransistorsKrotnev, Ivan 29 November 2013 (has links)
This thesis describes a novel concept for a field-effect transistor based on metallic channels. Latest research demonstrates that the bulk (3D) properties of many materials begin to change when confined to 2D sheets, or 1D nanowires. Particularly, the bandgap increases and the density of states decreases. In this work, this effect is explored further to demonstrate its application to field-effect transistors. Certain metals such as Gold and Silver in these dimensions have extremely low density of states in particular energy regions and through gate modulation can be partially depleted from electrons thus creating conditions for field-effect. A simulation study of Gold channel FET demonstrates ION/IOFF of 30 and superior current driving capability compared to the state-of-the art 22nm SiGe ETSOI as well as 30nm nanotube transistors.
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Novel Metallic Field-effect TransistorsKrotnev, Ivan 29 November 2013 (has links)
This thesis describes a novel concept for a field-effect transistor based on metallic channels. Latest research demonstrates that the bulk (3D) properties of many materials begin to change when confined to 2D sheets, or 1D nanowires. Particularly, the bandgap increases and the density of states decreases. In this work, this effect is explored further to demonstrate its application to field-effect transistors. Certain metals such as Gold and Silver in these dimensions have extremely low density of states in particular energy regions and through gate modulation can be partially depleted from electrons thus creating conditions for field-effect. A simulation study of Gold channel FET demonstrates ION/IOFF of 30 and superior current driving capability compared to the state-of-the art 22nm SiGe ETSOI as well as 30nm nanotube transistors.
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Scaling limits and opportunities of double-gate MOSFETSChen, Qiang 05 1900 (has links)
No description available.
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Fabrication de transistors monoélectroniques pour la détection de chargeRichard, Jean-Philippe January 2013 (has links)
Le transistor monoélectronique (SET) est un candidat que l'on croyait avoir la capacité de remplacer le transistor des circuits intégrés actuel (MOSFET). Pour des raisons de faible gain en voltage, d'impédance de sortie élevée et de sensibilité aux fluctuations de charges, il est considéré aujourd'hui qu'un hybride tirant profit des deux technologies est plus avantageux. En exploitant sa lacune d'être sensible aux variations de charge, le SET est davantage utilisé dans des applications où la détection de charge s'avère indispensable, notamment dans les domaines de la bio-détection et de l'informatique quantique. Ce mémoire présente une étude du transistor monoélectronique utilisé en tant que détecteur de charge. La méthode de fabrication est basée sur le procédé nanodamascène développé par Dubuc et al. [11] permettant au transistor monoélectronique de fonctionner à température ambiante. La température d'opération étant intimement liée à la géométrie du SET, la clé du procédé nanodamascène réside dans le polissage chimico-mécanique (CMP) permettant de réduire l'épaisseur des SET jusqu'à des valeurs de quelques nanamètres. Dans ce projet de maîtrise, nous avons cependant opté pour que le SET soit opéré à température cryogénique. Une faible température d'opération permet le relâchement des contraintes de dimensions des dispositifs. En considérant les variations de procédés normales pouvant survenir lors de la fabrication, la température d'opération maximale calculée en conception s'étend de 27 K à 90 K, soit une énergie de charge de 78 meV à 23 meV. Le gain du détecteur de charge étant dépendant de la distance de couplage, les résultats de simulations démontrent que cette distance doit être de 200 nm pour que la détection de charge soit optimale. Les designs conçus sont ensuite fabriqués sur substrat d'oxyde de silicium. Les résultats de fabrication de SET témoignent de la robustesse du procédé nanodamascène. En effet, les dimensions atteintes expérimentalement s'avèrent quasi identiques à celles calculées en conception. Les mesures électriques à basse température de SET fabriqués démontrent un blocage de Coulomb avec une énergie de charge de 10 meV et une température d'opération maximale de 10 K. Un effet de grille est aussi observé par l'application d'une tension sur la grille latérale et les électrodes d'un SET à proximité. Les paramètres extraits à partir du diamant de Coulomb sont en accord avec les géométries du transistor fabriqué, à l'exception de la capacité degrille et de couplage. Enfin, l'étude de la détection de charge est réalisée par simulation à partir de ces paramètres. Elle permet de conclure que la détection de charge peut être optimisée en augmentant les surfaces de couplage de l'électromètre.
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Intégration hybride de transistors à un électron sur un noeud technologique CMOSJouvet, Nicolas January 2012 (has links)
Cette étude porte sur l'intégration hybride de transistors à un électron (single-electron transistor, SET) dans un noeud technologique CMOS. Les SETs présentent de forts potentiels, en particulier en termes d'économies d'énergies, mais ne peuvent complètement remplacer le CMOS dans les circuits électriques. Cependant, la combinaison des composants SETs et MOS permet de pallier à ce problème, ouvrant la voie à des circuits à très faible puissance dissipée, et à haute densité d'intégration. Cette thèse se propose d'employer pour la réalisation de SETs dans le back-end-of-line (BEOL), c'est-à-dire dans l'oxyde encapsulant les CMOS, le procédé de fabrication nanodamascène, mis au point par C. Dubuc. Les avantages de ce procédé sont triples : capacité de créer des dispositifs SETs à large marge d'opération, répétabilité élevée, et compatibilité potentielle avec une fabrication en BEOL. Ce dernier point est particulièrement important. En effet, il ouvre la voie à la fabrication de nombreuses couches de SETs empilées les unes sur les autres et formant ainsi des circuits 3D, réalisées au-dessus d'une couche de CMOS. Ceci permettrait d'apporter une forte valeur ajoutée aux plaques de CMOS existantes. On présentera les réalisations obtenues par une adaptation du procédé nanodamascène à une fabrication en BEOL, en mettant en avant les limites rencontrées, et les perspectives d'améliorations. Des caractérisations électriques des dispositifs seront aussi présentées. Elles démontrent la fonctionnalité des dispositifs créés, et valident le transfert avec succès de la méthode nanodamascène à une fabrication en BEOL. Elles ont aussi permis d'identifier la présence d'un nombre élevé de pièges au coeur des dispositifs fabriqués. L'étude du potentiel des SETs fabriqués pour la réalisation de circuits hybride SET-CMOS a été faite au travers de simulations. D a ainsi été possible d'identifier les pistes à privilégier pour les réalisations futures de circuits hybrides.
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Effect of Dissipation on the Dynamics of Superconducting Single Electron TransistorsMeng, Shuchao January 2012 (has links)
In this thesis, I will present the experimental results of the dynamics of
superconducting single electron transistors (sSETs), under the influence of
tunable dissipation. The sSET, consisting of two dc SQUIDs in series and
the third gate electrode, is deposited onto a GaAs/AlGaAs heterostructure
which contains a two dimensional electron gas plane 100nm beneath the
substrate surface. The Josephson coupling energy, charging energy and
dissipation related Hamiltonian can all be tuned in situ, while keeping
others unchanged. We measured the switching current statistics and the
transport properties, as a function of the dissipation and gate charge at
different temperatures.
If the sSET is in the classical regime where phase is a good quantum
variable, we found that the switching current and corresponding Josephson
energy decrease as dissipation increases. Our observation agrees qualitatively
with the theoretical calculation of a single Josephson junction
with dominant Josephson energy, in a frequency dependent dissipative
environment where energy barrier decreases as dissipation increases in
thermally activated escape regime. This dissipation dependence result can
be understood as the consequence of a reduced quantum fluctuations in
the charge numbers.
Whereas in the charging regime, the switching current shows a 1e
periodicity with respect to gate charge, indicating a pronounced charging
effect. At a specific gate charge number, quantum fluctuations of the phase
variable are compressed as dissipation increases, resulting in an enhanced
switching current and Josephson energy. This result matches the theory of a sSET capacitively coupled to a dissipative environment qualitatively.
The temperature dependence of the switching current histogram indicates
the existence of both quantum and classical thermal phase diffusion.
Moreover, quantum charge fluctuations are minimized at the degeneracy
point, causing a sharp dip on the width of the switching current histogram.
For a sSET with comparable Josephson energy and charging energy,
quantum fluctuations of both phase and charge variables are significant.
The influence of dissipation on the dynamics of the device is distinct in the
classical and charging regimes. Dissipation compresses quantum phase
fluctuations in the charging regime, whereas reduces the quantum charge
fluctuations in the classical regime. The transition between these two
regimes is found to be determined by the tunnel resistance of the SQUID.
The competition between Josephson and charging energies, however, is
not the intrinsic parameter of this transition. Our results imply that a
detailed theoretical calculation of a sSET with comparable Josephson
coupling energy and charging energy under the influence of dissipation is
needed.
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High-Performance Polymer Semiconductors for Organic Thin-Film TransistorsSun, Bin January 2012 (has links)
A novel polymer semiconductor with side chains thermally cleavable at a low temperature of 200 °C was synthesized. The complete cleavage and removal of the insulating 2-octyldodecanoyl side chains were verified with TGA, FT-IR, and NMR data. The N-H groups on the native polymer backbone are expected to form intermolecular hydrogen bonds with the C=O groups on the neighboring polymer chains to establish 3-D charge transport networks. The resulting side chain-free conjugated polymer is proven to be an active p-type semiconductor material for organic thin film transistors (OTFTs), exhibiting hole mobility of up to 0.078 cm2V-1s-1. This thermo-cleavable polymer was blended with PDQT to form films that showed a higher performance than the pure individual polymers in OTFTs.
MoO3 or NPB was used as a hole injection buffer layer between the metal electrodes and the polymer semiconductor film layer in OTFT devices. This buffer layer improved hole injection, while its use in the OTFT, improved the field-effect mobility significantly due to better matched energy levels between the electrodes and the polymer semiconductor.
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