Anharmonicity in GaTe layered crystals

The temperature dependencies (10-300 K) of seven Raman-active mode frequencies in layered semiconductor gallium telluride have been measured in the frequency range from 25 to 300 cm -1. Softening and broadening of the optical phonon lines are observed with increasing temperature. Comparison between the experimental data and theories of the shift of the phonon lines during heating of the crystal showed that the experimental dependencies can be explained by contributions from thermal expansion and lattice anharmonicity. Lattice anharmonicity is determined to be due to three-phonon processes

Deposition of ZnO thin films by RF&DC magnetron sputtering on silicon and porous-silicon substrates for pyroelectric applications

In this study, the temperature response of ZnO thin film is investigated in an attempt to enhance its pyroelectric performance. The film is formed on PS and Si substrates utilizing RF&DC magnetron sputtering deposition technique. The outcome of study reveals a pyroelectric coefficient observed from ZnO film on PS which is 40 times higher than that on Si and a pyroelectric voltage as high as 2.4 V due to PS's profound effect on film formation, large surface to volume area and low thermal conductivity. Thus, this study can lead the way to a robust, reliable and more efficient pyroelectric operation of ZnO with employment of PS structure. © 2017 Elsevier B.V

Series resistance calculation for the metal-insulator-semiconductor Schottky barrier diodes

An accurate way of determining the series resistance R(s) of Schottky Barrier Diodes (SBDs) with and without the interfacial oxide layer using forward current-voltage (I-V) characteristics is discussed both theoretically and experimentally by taking into account the applied voltage drop across the interfacial layer V-i. For the experimental discussion, the forward bias I-V characteristics of the SBDs with and without the oxide layer fabricated by LEC (the Liquid-Encapsulated Czochralski) GaAs were performed. The SBD without the oxide layer was fabricated to confirm a novel calculation method. For the theoretical discussion, an expression of V-i was obtained by considering effects of the layer thickness and the interface state density parameters on forward bias I-V of the SBDs. The Value R(s) of the SBD with interfacial oxide layer was seen to be larger than that of the SBD without the interfacial oxide layer due to contribution of this layer to the series resistance. According to the obtained theoretical formula, the value of V-i for the SBD with the oxide layer was calculated and it was subtracted from the applied voltage values V and then the value of R(s) was recalculated. Thus, it has been shown that this new value of R(s) is in much closer agreement with that determined for the SBD without the oxide layer as predicted. Furthermore, the curves of the interface states energy distribution of each sample are determined. It was concluded that the shape of the density distribution curve and order of magnitude of the density of the interface states in the considered energy range are in close agreement with those obtained by others for Au/n-GaAs Schottky diodes by Schottky capacitance spectroscopy

Effect of series resistance on the forward current-voltage characteristics of Schottky diodes in the presence of interfacial layer

In order to make an accurate determination of Schottky diode parameters such as the ideality factor, the barrier height and the series resistance [using forward current-voltage (I-V) characteristics in the presence of an interfacial layer], a novel calculation method has been developed by taking into account the applied voltage drop across the interfacial layer (V-i). The parameters obtained by accounting for the voltage drop V,have been compared with those obtained without considering the above voltage drop. To examine the consistency of this approach, the comparison has been made by means of Schottky diodes fabricated on a n-type semiconductor substrate with different bulk thickness. It is shown that the voltage drop across the interfacial layer will increase the ideality factor and the voltage dependence of the I-V characteristics. In addition, it is shown that the series resistance value increases as the semiconductor bulk thickness has been increased