Search results for "Semiconductor"
showing 10 items of 974 documents
Monte Carlo study of diffusion noise reduction in GaAs operating under periodic conditions
2009
The effects of an external correlated source of noise on the intrinsic carrier noise in a low-doped GaAs bulk, operating under periodic conditions, are investigated. Numerical residts confirm that the dynamical response of electrons driven by a high-frequency periodic electric field receives a benefit by the constructive interplay between the fluctuating field and the intrinsic noise of the system. In particidar, in this contribute we show a nonmonotonic behavior of the integrated spectral density, which value critically depends on the correlation time of the external noise source.
Semiconductor electrochemistry approach to passivity and passivity breakdown of metals and metallic alloys
2004
AbstractA critical appraisal of the use of the theory of semiconductors in characterising passive films on metals and alloys is provided, with special emphasis on the use of Mott-Schottky theory for the location of characteristic energy levels of the passive film-electrolyte junction. Some inconsistencies between theory and experimental results in the case of thin passive films are discussed together with possible alternative ways for overcoming such problems. The role of semiconducting properties in determining the pitting behaviour of passive films on W in solutions containing halide is presented and discussed. The validity of a recently proposed correlation between the solid state proper…
Optimization of quasi-hemispherical CdZnTe detectors by means of first principles simulation
2023
AbstractIn this paper we present the development of quasi-hemispherical gamma-ray detectors based on CdZnTe. Among the possible single-polarity electrode configurations, such as coplanar, pixelated, or virtual Frisch-grid geometries, quasi-hemispherical detectors are the most cost-effective alternative with comparable raw energy resolution in the high and low energy range. The optimal configuration of the sensor in terms of dimension of the crystals and electrode specifications has been first determined by simulations, and successively validated with experimental measures. Spectra from different sources have been acquired to evaluate the detectors performances. Three types of detectors with…
An ab initio study of the polytypism in InP
2016
AbstractThe existence of polytypism in semiconductor nanostructures gives rise to the appearance of stacking faults which many times can be treated as quantum wells. In some cases, despite of a careful growth, the polytypism can be hardly avoided. In this work, we perform an ab initio study of zincblende stacking faults in a wurtzite InP system, using the supercell approach and taking the limit of low density of narrow stacking faults regions. Our results confirm the type II band alignment between the phases, producing a reliable qualitative description of the band gap evolution along the growth axis. These results show an spacial asymmetry in the zincblende quantum wells, that is expected …
Fast photoconduction in the highly ordered columnar phase of a discotic liquid crystal
1994
THE search for organic materials suitable for electronic applica-tions dates back to the early 1950s. But the only organic systems known so far to show electronic charge-carrier mobilities comparable to the amorphous inorganic semiconductors that are the main-stay of the microelectronics industry are zone-refined organic single crystals1–4. Single crystals are difficult and costly to process, however, and are not suitable for device applications. Here we show that a highly ordered columnar (stacked) phase of disk-like organic molecules can exhibit high mobilities for photoinduced charge carriers, of the order of 0.1 cm2 V-1 s-1—higher than for any organic material other than single-crystal …
Defect reactions of implanted Li in ZnSe observed by β-NMR
2001
Abstract Using β-radiation detected nuclear magnetic resonance (β-NMR), we investigated the microscopic behavior of implanted 8 Li in nominally undoped ZnSe crystals. From the temperature-dependent amplitudes of high-resolution NMR spectra we conclude a gradual interstitial-to-substitutional site change between 200 and 350 K . This is in accordance with earlier emission channeling results. We argue that this conversion proceeds via Lii++VZn2−→LiZn− and involves implantation related Zn vacancies.
Role of Ge nanoclusters in the performance of photodetectors compatible with Si technology
2013
In this work, we investigate the spectral response of metal-oxide- semiconductor photodetectors based on Ge nanoclusters (NCs) embedded in a silicon dioxide (SiO2) matrix. The role of Ge NC size and density on the spectral response was evaluated by comparing the performance of PDs based on either densely packed arrays of 2 nm-diameter NCs or a more sparse array of 8 nm-diameter Ge NCs. Our Ge NC photodetectors exhibit a high spectral responsivity in the 500-1000 nm range with internal quantum efficiency of ~ 700% at - 10 V, and with NC array parameters such as NC density and size playing a crucial role in the photoconductive gain and response time. We find that the configuration with a more…
Photocatalytic activity of binary and ternary SnO2–ZnO–ZnWO4 nanocomposites
2015
Binary and ternary SnO2-ZnO-ZnWO4 nanocomposites were prepared by a sol-gel route. The photocatalytic activity of the samples was evaluated through the decomposition of 4-nitrophenol and partial oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde. All the mixed catalysts revealed higher photoactivity than bare ZnO, SnO2 or ZnWO4 and the best performances were exhibited by the binary nanocomposites. The high photocatalytic activity was explained by the presence of heterojunctions among different semiconductors that enhance the separation of the photogenerated electron-hole pairs, hindering their recombination. As a general consideration, an essential role was played by the electronic feat…
A new CdTe/ZnO columnar composite film for Eta-solar cells
2002
Abstract First results of CdTe deposition on ZnO films consisting of free standing single crystalline columns of several micrometers height and ∼100– 200 nm diameter are presented. The ZnO films have been obtained by electrochemical deposition on conductive glass. Morphology, structural and optical properties of the nanostructured columnar CdTe/ZnO composite films have been studied. The cadmium telluride ( 40 nm thick) deposited by vapor-phase epitaxy under dynamical vacuum is lining the ZnO columns as a continuous smooth thin film with conformal coverage. The polycrystalline CdTe layer is a mixture of cubic and hexagonal phases and is semiconductor with a direct band gap optical transition…
Memory effects in MOS devices based on Si quantum dots
2003
Silicon quantum dots have been deposited on top of a 3-nm tunnel oxide by Low Pressure Chemical Vapour Deposition (LPCVD) and coated with a 7-nm Chemical Vapour Deposited (CVD) oxide. This stack was then incorporated in Metal-Oxide-Semiconductor structure and used as floating gate of a memory cell. The presence of 3 nm of tunnel oxides allows the injection of the charge by direct tunnel (DT) using low voltages for both program and erase operations. The charge stored in the quantum dots is able to produce a well-detectable flat band shift in the capacitors or, equivalently, a threshold voltage shift in the transistors. Furthermore, due to the presence of SiO 2 between the grains, the lateral…