Papers by Keyword: Semiconductor Materials

Abstract: Thermoelectric materials are useful for various application in daily life. Their application such as sensors, generators and electronic components, making thermoelectric materials widely studied. Antiperovskite compounds that can have semiconducting behaviour is probable candidate for thermoelectric materials. In this article, thermoelectric properties of anti-perovskite X₃SiO (X = Sr and Ba) were investigated using density functional theory (DFT) method and Boltzmann Transport Equations (BTE). Electronic properties such as band structure, partial density of states were computed using the generalized gradient approximation with Perdew-Burke-Ernzerhof (GGA-PBE) functional in CASTEP code. The thermoelectric properties such as Seebeck coefficient, electrical conductivity, and power factor are calculated using BoltzTraP code that utilised BTE. The calculated band structures of Ba₃SiO and Sr₃SiO show that these compounds having semiconductor behaviour with direct band gap of 0.44 and 0.43 eV respectively at Γ-Γ k-point. It was found that Ba₃SiO is a better candidate for thermoelectric materials due to its higher Seebeck coefficient (-4.90 10^-4 V/K) at room temperature compared to calculated Seebeck coefficient (-5.84 10^-4 V/K) of Sr₃SiO. The power factor value of Ba₃SiO which is 2.96 x 10^-4 W/mK² is also higher compared to power factor of Sr₃SiO at 7.12 x 10^-7 W/mK² at room temperature.

Abstract: The overall efficiency of a PV system is strongly affected by the PV cell raw materials. Since a reliable renewable energy source is expected to produce maximum power with longest lifetime and minimum errors, a critical aspect to bear in mind is the occurrence of PV faults according to raw material types. The different failure scenarios occurring in PV system, decrease its output power, reduce its life expectancy and ban the system from meeting load demands, yielding to severe consecutive blackouts. This paper aims first to present different core materials types, material based fault occurring on the PV cell level and consequently the fault detection techniques corresponding to each fault type.

Abstract: We have computed the Mulliken’s population (MP) to deduce charge transfer from WO in semiconducting WO3 using density functional theory (DFT) within pseudopotential scheme. In the DFT scheme, second order generalized gradient approximation for exchange and correlation has been implemented for the first time. The MP data show significant difference in charge transfer between W and six non–equivalent O atoms. In addition, the full potential linearized augmented plane wave method has been applied to compute the partial and total density of states. The MP data have also been explained in terms of partial DOS.

Abstract: AgCl microparticle materials, with novel heart-like morphology, were successfully prepared by means of a simple solution phase route, in which a small amount of hydrochloric acid, ethylene and PVP were introduced to the conventional polyol process. The obtained microparticle materials were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and UV-Vis absorption spectrum. SEM images show that the obtained AgCl microparticle materials have heart-like morphology with an average diameter of 3 um. The influence of different reaction times on size and morphology of the microparticle materials were also investigated. A possible growth mechanism of AgCl microparticle materials has been proposed on the basis of experimental results and analysis. The as-prepared AgCl microparticle materials would find possible potential applications in photocatalytic fields.

Abstract: The thermal expansion of a novel semiconductor material, mercury indium telluride (MIT) grown by vertical Bridgman (VB) method, was measured from room temperature till 573K by two methods, i.e. Macroscopic dilatometric and X-ray measurements. It is found that the macroscopic expansion is quite different from the expansion of the lattice (micro-expansion). The macroscopic expansion is lower than micro-expansion in the temperature range of 303-425.5K and has a minimum of -0.14% linear expansion, while the macro-expansion becomes larger than micro-expansion in the temperature higher than 425.5K. The former may be due to the effects of the existing neutral vacancies. The latter may result from the influence of thermal-activated vacancies on the lattice.

Abstract: Cu-Se compound powders are synthesized by hydrothermal co-reduction from CuSO4•5H2O and SeO2 in deionized water at 120～200 °C. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, the CuSe phase can be synthesized at 120,150,180 and 200 °C, however, the purity phases become more with the temperature decreasing. It indicates that the reaction is more incomplete at lower temperature. Hexagonal flakes with side length 100～400 nm can be observed in the products at 150,180 and 200 °C, among which only the product prepared at 180 °C has the hexagonal flakes with good dispersity and homogeneous size with 200 nm length.

Abstract: Ni-Se powders synthesized by hydrothermal co-reduction method from NiCl2.6H2O and SeO2 at 95～220 °C. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, Ni0.85Se can be synthesized at 95～220 °C while noticeable impurities appeared at lower reaction temperatures. The products with single-phase Ni0.85Se obtained at 200 and 220 °C show hollow sphere structures with diameters of about 150 ~ 700 nm, which have complete and regular shape but no holes.

Abstract: The majority of integrated circuits are built on silicon wafers. To manufacture high-quality silicon wafers, a series of processes are needed. After a wire sawing process slices silicon ingots into wafers, grinding processes can be used to flatten the sliced wafers. This paper reports three experimental investigations on wafer grinding. The first investigation was to study the effectiveness of soft-pad grinding in removing the wire-sawing induced waviness. The second was to explore the capability of grinding in achieving super flatness. The third was to study the effects of grinding parameters on wafer flatness.

Abstract: The use of semiconductor materials in radiation processing, radiation therapy and diagnostics, and detection of cosmic radiation motivated development of numerical methods for its radiological characterization. This paper presents the application of the Monte Carlo method using the FOTELP-2K4 code for radiological characterization of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeter. The advantages of MOSFET dosimeters include small size, immediate readout, and ease of use for a wide photon energy range. In order to determine the dosimeter response accurately, distribution of the absorbed dose in the MOSFET structure has been investigated. Our results show that the absorbed dose distribution calculated by the presented simulation model compares well with the published data.

Abstract: Research achievements in a high speed attraction type magnetic levitation vehicle experimental system are reported. The high speed attraction type magnetic levitation vehicle constitutes a typical long stator linear synchronous motor. The study on levitation and propulsive electromagnetic fields is of great importance and is studied. Owing to the influence of the stator grooves and the material discontinuousness, the magnetic field distribution is very complex to be analyzed in analytical forms. The magnetic fields in the air gap are determined using the finite element method. The levitation force and thrust produced by the levitation magnetic field and the propulsive magnetic field are calculated. They are found to vary following the change of the air gap and exciting current. A magnetic field strength measurement system based on a hall sensor is designed. Experimental results are compared with the results from the magnetic field analysis.