The model of the equations of generalized thermoelasticity in a semi-conducting medium with two-temperature is established. The entire elastic medium is rotated with a uniform angular velocity. The formulation is applied under Lord-Schulman theory with one relaxation time. The normal mode analysis is used to obtain the expressions for the considered variables. Also some particular cases are discussed in the context of the problem. Numerical results for the considered variables are obtained and illustrated graphically. Comparisons are also made with the results predicted in the absence and presence of rotation as well as two-temperature parameter.
This paper presents the current state of a photoconductive semiconductor switch engineering. A photoconductive semiconductor switch is an electric switch with its principle of operation based on the phenomenon of photoconductivity. The wide application range, in both low and high-power devices or instruments, makes it necessary to take design requirements into account. This paper presents selected problems in the scope of designing photoconductive switches, taking into account, i.e. issues associated with the element trigger speed, uniform distribution of current density, thermal resistance, operational lifespan, and a high, local electric field generated at the location of electrodes. A review of semiconductor materials used to construct devices of this type was also presented.
Sensors designed by Polish engineers help detect traces of life beyond Earth. Adam Piotrowski of Vigo System tells us what else these devices can do.
The paper presents the results of investigations concerning the application of zinc oxide - a wideband gap semiconductor in optical planar waveguide structures. ZnO is a promising semiconducting material thanks to its attractive optical properties. The investigations were focused on the determination of the technology of depositions and the annealing of ZnO layers concerning their optical properties. Special attention was paid to the determination of characteristics of the refractive index of ZnO layers and their coefficients of spectral transmission within the UV-VIS-NIR range. Besides that, also the mode characteristics and the attenuation coefficients of light in the obtained waveguide structures have been investigated. In the case of planar waveguides, in which the ZnO layers have not been annealed after their deposition, the values of the attenuation coefficient of light modes amount to a~ 30 dB/cm. The ZnO layers deposited on the heated substrate and annealed by rapid thermal annealing in an N2 and O2 atmosphere, are characterized by much lower values of the attenuation coefficients: a~ 3 dB/cm (TE0 and TM0 modes). The ZnO optical waveguides obtained according to our technology are characterized by the lowest values of the attenuation coefficients a encountered in world literature concerning the problem of optical waveguides based on ZnO. Studies have shown that ZnO layers elaborated by us can be used in integrated optic systems, waveguides, optical modulators and light sources.
In recent years organic semiconductors have been given attention in the field of active materials for gas sensor applications. In the paper the investigations of the optoelectronic sensor structure of ammonia were presented. The sensor head consists of polyaniline and Nafion layers deposited on the face of the telecommunication optical fiber. The elaborated sensor structure in the form of Fabry-Perot interferometer is of the extremely small dimension – its thickness is of the order of 1 um. Many sensor structures of diffierent combinations of the polyaniline and Nafion layers were constructed and investigated. The optimal solution seems to be the structures with small number of polianiline layers (up to three).
The presented article is a report on progress in photovoltaic devices and material processing. A cadmium telluride solar cell as one of the most attractive option for thin-film polycrystalline cell constructions is presented. All typical manufacturing steps of this device, including recrystalisation and junction activation are explained. A new potential field of application for this kind of device - the BIPV (Building Integrated Photovoltaic) is named and discussed. All possible configuration options for this application, according to material properties and exploitation demands are considered. The experimental part of the presented paper is focused on practical implementation of the high- temperature polymer foil as the substrate of the newly designed device by the help of ICSVT (Isothermal Close Space Vapour Transport) technique. The evaluation of the polyester and polyamide foils according to the ICSVT/CSS manufacturing process parameters is described and discussed. A final conclusion on practical verification of these materials is also given.
Five new derivatives of 4,6-di(thiophen-2-yl)pyrimidine (DTP) were designed by structural modification with the aim to tune the electro-optical and charge transfer properties. The effect of oligocene and oligocenothiophene incorporation/substitution was investigated on various properties of interests. The smaller hole reorganization energy revealed that compounds 1-5 might be good hole transfer contenders. The smaller hole reorganization energy of newly designed five DTP derivatives than the pentacene showed that prior compounds might be good/comparable hole transfer materials than/to that of pentacene. The computed electron reorganization energy of DTP derivatives 1-5 are 124, 185, 93, 95 and 189 meV smaller than the meridional-tris (8-hydroxyquinoline) aluminum (mer-Alq3) illuminating that electron mobility of these derivatives might be better/comparable than/to referenced compound.
A revision of the standard approach to characterization of thin-semiconductor-layer Hall samples has been proposed. Our results show that simple checking of I(V) curve linearity at room temperature might be insufficient for correct determination of bias conditions of a sample before measurements of Hall effect. It is caused by the nonlinear behaviour of electrical contact layers, which should be treated together with the tested layer a priori as a metal-semiconductor-metal (MSM) structure. Our approach was examined with a Be-doped p-type InAs epitaxial layer, with four gold contacts. Despite using full high-quality photolithography a significant asymmetry in maximum differential resistance (Rd) values and positions relative to zero voltage (or current) value was observed for different contacts. This suggests that such characterization should be performed before each high-precision magneto-transport measurement in order to optimize the bias conditions.
Variable speed and low voltage electrical drives are commonly operated by frequency converters. According to recent developments, there is a trend in the area of semi-conductors, that switching frequency and voltage slew rate will increase significantly. The aim of these semiconductors is to reduce the switching losses and to increase the switching frequency, which enables to reduce the size of passive components in the power- electric circuit. This results in less material effort and lower cost, for the power electronic component. However, electric motors operated by high slew rate inverters show problems in the winding insulation, which have to be analyzed. Such problems are well known for high voltage machines. Due to the increasing slew rate, this problematic occurs in low voltage machines nowadays as well. Here, the influence of fast switching semiconductors on the winding insulation system is studied, using accelerated ageing tests with fast switching high-voltage generators.
In this paper an analysis of the surface properties of (Ti,Pd,Eu)Ox thin films prepared by magnetron sputtering has been described. In particular, the results of composition and structure investigations were studied in relation to the surface state and optical properties. It was found that (Ti,Pd,Eu)Ox film was nanocrystalline and had a rutile structure. The average crystallites size was equal to 7.8 nm. Films were homogeneous and had densely packed grains. Investigation of the surface properties by XPS showed that titanium was present at 4+ state (in the TiO2form), palladium occurred as PdO2(also at 4+ state), while europium was in Eu2O3form (at 3+ state). In comparison with the unmodiffied TiO2, the coating with Pd and Eu additives had a rather high transparency (approx. 47%) in the visible light range, its optical absorption edge was shifted towards into the longer wavelengths (from 345 nm to 452 nm), and the width of optical energy gap Egopt was nearly twice lower (1.82 eV). Besides, the resistivity of (Ti,Pd,Eu)Ox at room temperature was 1×103 Wcm. In the case of the film as-deposited on Si substrate (p-type) the generation of photocurrent as a response to light beam excitation (λexc = 527 nm) was observed.
This paper is an analysis of determination possibility of the optical absorption coefficient spectra of thin semiconductor layers from their normalized photoacoustic amplitude spectra. Influence of multiple reflections of light in thin layers on their photoacoustic and optical absorption coefficient spectra is presented and discussed in detail. Practical formulae for the optical absorption coefficient spectrum as a function of the normalized photoacoustic amplitude spectrum are derived and presented. Next, they were applied for computations of the optical absorption coefficient spectra of thin In2S3 thin layers deposited on a glass substrate. This method was experimentally verified with the optical transmission method.
The Ag8SnSe6 argyrodite compound was synthesized by the direct melting of the elementary Ag, Sn and Se high purity grade stoichiometric mixture in a sealed silica ampoule. The prepared polycrystalline material was characterized by the X-ray diffraction (XRD), visible (VIS) and near-infrared (NIR) reflection and photoluminescence (PL) spectroscopy. XRD showed that the Ag8SnSe6 crystallizes in orthorhombic structure, Pmn21 space group with lattice parameters: а = 7.89052(6) Å, b = 7.78976(6) Å, c = 11.02717(8) Å. Photoluminescence spectra of the Ag8SnSe6 polycrystalline wafer show two bands at 1675 nm and 1460 nm. Absorption edge position estimated from optical reflectance spectra is located in the 1413–1540 nm wavelength range.
Currently, work is underway to manufacture and find potential applications for a photoconductive semiconductor switch made of a semi-insulating material. The article analyzes the literature in terms of parameters and possibilities of using PCSS switches, as well as currently used switches in power and pulse power electronic system. The results of laboratory tests for the prototype model of the GaP-based switch were presented and compared with the PCSS switch parameters from the literature. The operating principle, parameters and application of IGBT transistor, thyristor, opto-thyristor, spark gap and power switch were presented and discussed. An analysis of the possibilities of replacing selected elements by the PCSS switch was carried out, taking into account the pros and cons of the compared devices. The possibility of using the currently made PCSS switch from gallium phosphide was also discussed.
The effect of modifications in epi-side (top) gold metallization on a thermal performance and on power roll-over of blue-vio- let III-N-based p-up edge-emitting ridge-waveguide laser diode (RW EEL) was explored in this paper. The calculations were carried out using a two-dimensional self-consistent electrical-thermal model combined with a simplified optical model tuned to a RW EEL fabricated in the Institute of High Pressure Physics (Unipress). Our results suggest that with proper modifica- tions in the III-N-based RW EEL, excluding modifications in its inner structure, it is possible to considerably improve the thermal performance and, thus, increase the maximal output power.