Search results for "Field effect"
showing 10 items of 44 documents
Impact of contact resistance on the electrical properties of MoS2 transistors at practical operating temperatures
2017
Molybdenum disulphide (MoS2) is currently regarded as a promising material for the next generation of electronic and optoelectronic devices. However, several issues need to be addressed to fully exploit its potential for field effect transistor (FET) applications. In this context, the contact resistance, RC, associated with the Schottky barrier between source/drain metals and MoS2 currently represents one of the main limiting factors for suitable device performance. Furthermore, to gain a deeper understanding of MoS2 FETs under practical operating conditions, it is necessary to investigate the temperature dependence of the main electrical parameters, such as the field effect mobility (μ) an…
Predictive dead time controller for GaN-based boost converters
2017
A dynamic dead time controller is presented, specifically intended to operate in synchronous boost converters based on GaN field-effect transistor switches. These transistors have a reduced stored charge with respect to silicon metal–oxide–semiconductor field-effect transistors with similar breakdown voltage and series resistance, and can operate at higher frequencies with reduced switching losses. On the other hand, the voltage drop in reverse conduction is typically more than doubled with respect to silicon devices resulting in relevant power losses during the free-wheeling phases. Therefore, dynamic control of dead time can be profitably applied even in converters operating in the tens o…
Carrier localization effect in polarized InGaN multiple quantum wells
2005
Carrier localization effects in polarized InGaN/GaN multiple quantum wells (MQWs) were investigated as a function of well width, d, and In content, x. Using photoreflectance (PR), photoluminescence (PL), PL excitation (PLE), selective excitation of PL, PL excitation power, and time-resolved PL spectroscopy, the dominance of the localization effect against the built-in field effect on carrier recombination dynamics in InxGa1–xN MQWs of different well width (d = 2.0–4.0 nm, x ≈ 0.15) and In content (x ≈ 0.22–0.27, d = 2.5 nm) was revealed. Based on the modeling of the PL spectra by Monte Carlo simulation of exciton hopping and the spectroscopic reference provided by PR, increased In content a…
Electrochemical Fabrication of Inorganic/Organic Field Effect Transistor
2010
After discovery of conducting polymers and the possibility to modify their electrical properties (from insulating to metallic-like behaviour) by doping and a careful choice of the processing conditions, a large amount of research effort has been devoted to the theoretical understanding of their solid state properties as well as to exploit the possible application of conducting polymers in many technological fields including: large area organic electronics, polymer photovoltaic cell and sensors (1-2). Organic thin-film transistors appears very promising for the development of low cost, flexible and disposable plastic electronics. In order to reduce the operating voltage it has been suggested…
Saturated absorption spectroscopy: elimination of crossover resonances by use of a nanocell
2007
It is demonstrated that velocity selective optical pumping/saturation resonances of reduced absorption in a Rb vapor nanocell with thickness \textit{L=} $\lambda $, 2$\lambda $, and 3$\lambda $ (resonant wavelength $\lambda $ = 780 nm) allow the complete elimination of crossover (CO) resonances. We observe well pronounced resonances corresponding to the F$_{g}=3$ $\to $ F$_{e}=2,3,4$ hyperfine transitions of the $^{85}$Rb D$_{2}$ line with linewidths close to the natural width. A small CO resonance located midway between F$_{g}=3$ $\to $ F$_{e}=3$ and F$_{g}=3$ $\to$ F$_{e}=4$ transitions appears only for \textit{L} = 4$\lambda $. The D$_{2}$ line ($\lambda $ = 852 nm) in a Cs nanocell exhi…
Dual Substituent Parameter Modeling of Theoretical, NMR and IR Spectral Data of 5-Substituted Indole-2,3-diones
2002
Correlations of AM1 and PM3 theoretical data, 13C-NMR substituent chemical shifts (13C-SCS) and IR carbonyl group wave numbers [ν(C3â•ÂO)] were studied using dual substituent parameter (DSP) models for 5-substituted indole-2,3-diones. For the C7 atom a reverse substituent effect attributed to extended À-polarization was observed. On the other hand, the DSP approaches for the C3 atom showed normal substituent effects with some contribution of reverse effect supported strongly by 13C-SCS correlations. In the ν(C3â•ÂO) and p(C3â•ÂO) DSP correlations the field effect contribution predominates over the resonance effect, which justifies the using of earlier suggested vibrational cou…
Josephson junctions and superconducting field effect transistors based on epitaxial Bi2Sr2Can-1CunO2(n+2) thin films
1998
Abstract Josephson junctions based on thin films of the Bi2Sr2Ca2Cu3O10+δ compound show IcRn products compatible with YBa2Cu3O7−δ samples. Using quasiparticle tunneling experiments we found evidence for a superconductor–insulator–superconductor tunneling process via localized states in the barrier. The Bi2Sr2CaCu2O8+δ compound is investigated regarding possible applications in superconducting field effect devices. We present thin films of four unit cells thickness that are superconducting at 58 K. An inverted metal–insulator–superconductor structure was prepared. From the modulation of the normal state resistance we estimate a carrier density of 7×1019 cm−3 for a superconducting sample. The…
Layout influence on microwave performance of graphene field effect transistors
2018
The authors report on an in-depth statistical and parametrical investigation on the microwave performance of graphene FETs on sapphire substrate. The devices differ for the gate-drain/source distance and for the gate length, having kept instead the gate width constant. Microwave S -parameters have been measured for the different devices. Their results demonstrate that the cut-off frequency does not monotonically increase with the scaling of the device geometry and that it exists an optimal region in the gate-drain/source and gate-length space which maximises the microwave performance.
Carbon nanotube field-effect devices with asymmetric electrode configuration by contact geometry
2014
We have studied experimentally the conductive properties of single walled carbon nanotube (SWNT) based field-effect type devices, with different contact geometries at the connecting electrode. The device designs are asymmetric with one end of the SWNT having the metal electrode deposited on top and immersing it, while at the other end, the SWNT is on top of the electrode. The devices were made with either gold or palladium as electrode materials, of which the latter resulted in different behavior of the different contact types. This is argued to be caused by the existence of a thin insulating layer of surface adsorbents on the palladium, possibly Pd5O4, the effect of which is enhanced by th…
Aligned microcontact printing of biomolecules on microelectronic device surfaces
2001
Microcontact printing (/spl mu/CP) of extracellular matrix proteins is a fascinating approach to control cell positioning and outgrowth, which is essential in the development of applications ranging from cellular biosensors to tissue engineering. Microelectronic devices can be used to detect the activity from a large number of recording sites over the long term. However, signals from cells can only be recorded at small sensitive spots. Here, the authors present an innovative setup to perform aligned /spl mu/CP of extracellular matrix proteins on microelectronic devices in order to guide the growth of electrogenic cells specifically to these sensitive spots. The authors' system is based on t…