J.F. Yang

Manufacture, microstructure and mechanical properties of WTaN nano-structured hard films

Abstract W 1− x Ta x N y ( x xa0=xa00–0.95) hard films were deposited on Si substrates using reactive direct current magnetron sputtering. The effect of tantalum concentration on phase composition, microstructure, surface morphology, adhesion strength, and hardness of the films has been studied by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, nano-indenter, and scratch tester. It was found that regardless of tantalum concentration all the W 1− x Ta x N y films show face centered cubic structure, and form W Ta N solid solution. The hardness and Youngs’ modulus of W 1− x Ta x N y films initially increase and then decrease with increasing tantalum concentration, after passing the maximum value of 38xa0GPa and 360xa0GPa at x xa0=xa00.31, respectively. The adhesion strength of coating to silicon substrate is in the range of 27–35xa0N, no obvious variation trend of adhesion strength with tantalum concentration was observed.

A self-powered sensitive ultraviolet photodetector based on epitaxial graphene on silicon carbide*

A self-powered graphene-based photodetector with high performance is particularly useful for device miniaturization and to save energy. Here, we report a graphene/silicon carbide (SiC)-based self-powered ultraviolet photodetector that exhibits a current responsivity of 7.4 mA/W with a response frequency of over a megahertz under 325-nm laser irradiation. The built-in photovoltage of the photodetector is about four orders of magnitude higher than previously reported results for similar devices. These favorable properties are ascribed to the ingenious device design using the combined advantages of graphene and SiC, two terminal electrodes, and asymmetric light irradiation on one of the electrodes. Importantly, the photon energy is larger than the band gap of SiC. This self-powered photodetector is compatible with modern semiconductor technology and shows potential for applications in ultraviolet imaging and graphene-based integrated circuits.