Search results for "semiconductor"
showing 10 items of 974 documents
Nonlinear vibrations and hysteresis of micromachined silicon resonators designed as frequency-out sensors
1987
Experimental observation of nonlinear vibrations and hysteresis of micromachined silicon resonators is reported. The experimental results are explained using a simple model in which the restoring force acting in the resonator contains a small cubic term. The effects will impose a limit to the maximum amplitude which can be excited while still maintaining reliability of these devices as frequency-out sensors.
Plasmonic layers based on Au-nanoparticle-doped TiO2 for optoelectronics: structural and optical properties.
2013
The anti-reflective effect of dielectric coatings used in silicon solar cells has traditionally been the subject of intensive studies and practical applications. In recent years the interest has permanently grown in plasmonic layers based on metal nanoparticles, which are shown to increase light trapping in the underlying silicon. In the present work we have combined these two concepts by means of in situ synthesis of Au nanoparticles in a dielectric matrix (TiO2), which is commonly used as an anti-reflective coating in silicon solar cells, and added the third element: a 10–20% porosity in the matrix. The porosity is formed by means of a controllable wet etching by low concentration HF. As …
Efficiency comparison between SiC- and Si-based active neutral-point clamped converters
2015
This paper presents an efficiency comparison between silicon-carbide technology and silicon technology. In order to achieve this, the efficiency of an active neutral-point clamped converter built up with silicon carbide power-devices is compared with the efficiency of an active neutral-point clamped converter built up with silicon power-devices, under a particular operating mode and a particular selection of devices. Firstly, overall losses of both converters are estimated. Then, experimental tests are carried out to measure their overall losses and efficiency. Finally, experimental results are compared with the estimations to support the analysis. The efficiency of the SiC converter is hig…
Modelling and analysis of the influence of solar spectrum on the efficiency of photovoltaic modules
2021
Abstract The article presents the influence of changes in the solar radiation spectrum distribution on the properties of various photovoltaic modules, with particular emphasis on the scattered component. We compared the relative efficiency of the photovoltaic modules based on various semiconductor absorbers during bright and sunny, and cloudy summer days. Additionally, we presented the impact of the module tilt angle on the magnitude of the surface incident scattered component and on the efficiency of the module. The solar spectra for various weather conditions were estimated using specialised computer programmes,such as SolarSpectrum or SMARTS2, and we present here the validation results f…
High Resolution X-Ray Spectroscopy with Compound Semiconductor Detectors and Digital Pulse Processing Systems
2012
The advent of semiconductor detectors has revolutionized the broad field of X-ray spectroscopy. Semiconductor detectors, originally developed for particle physics, are now widely used for X-ray spectroscopy in a large variety of fields, as X-ray fluorescence analysis, X-ray astronomy and diagnostic medicine. The success of semiconductor detectors is due to several unique properties that are not available with other types of detectors: the excellent energy resolution, the high detection efficiency and the possibility of development of compact detection systems. Among the semiconductors, silicon (Si) detectors are the key detectors in the soft X-ray band (15 keV) and will continue to be the c…
Hard X-Ray Response of Pixellated CdZnTe Detectors
2009
In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10x10x1 and 10x10x2 mm3 single crystals) have an anode layout based on an array of 256 pixels with a …
Lattice Instability and Competing Spin Structures in the Double Perovskite InsulatorSr2FeOsO6
2013
The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron-osmium layers along the tetragonal c axis. Neutron powder diffraction experiments, 57Fe Mossbauer spectra, and density functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example of a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom.
Doping dependence of spin dynamics of drifting electrons in GaAs bulks
2010
We study the effect of the impurity density on lifetimes and relaxation lengths of electron spins in the presence of a static electric field in a n-type GaAs bulk. The transport of electrons and the spin dynamics are simulated by using a semiclassical Monte Carlo approach, which takes into account the intravalley scattering mechanisms of warm electrons in the semiconductor material. Spin relaxation is considered through the D'yakonov-Perel mechanism, which is the dominant mechanism in III-V semiconductors. The evolution of spin polarization is analyzed by computing the lifetimes and depolarization lengths as a function of the doping density in the range 10^{13} - 10^{16} cm^{-3}, for differ…
Recent developments in the manipulation of magnetic domain walls in CoFeB–MgO wires for applications to high-density nonvolatile memories
2015
Abstract The recent discovery that magnetic domain walls can be moved under a small current without any magnetic field opens a perspective for a paradigm shift in mass storage design. However, several fundamental questions must be answered before the technology can be considered feasible. This review covers the current understanding of domain wall (DW) propagation in CoFeB–MgO structures with perpendicular magnetic anisotropy. These films exhibit a very low density of pinning centers and can be integrated in Magnetic Tunnel Junctions, making them very promising for manipulating multiple domain walls in ultra-high-density spintronic devices. Several important issues are addressed: the physic…
Phonons of hexagonal BN under pressure: Effects of isotopic composition
2021
Raman scattering experiments on isotopically enriched hexagonal boron nitride have been performed under pressure up to 11 GPa at room temperature. The sublinear increase of the Raman-active E2g mode frequencies has been characterized. The pressure behavior has been analyzed by means of a bond-stiffness–bond-length scaling parameter γ which takes into consideration the vast differences in a- and c-axis compressibilities. The interlayer shear mode exhibits a γ parameter similar to that of graphite, and the mode frequency in isotopically pure samples separates faster at low pressures as a result of van der Waals interactions. Because of the extremely low a-axis compressibility, the intralayer …