The process for preparing MX2 (M=Mo,W; X=Se,S) single crystal

The layered semiconductor compound, as transition metal dichalcogenide family MX2 (M=Mo, W, X=S, Se) had stirred common interesting in solar energy conversion for its special photoelectronic properties. The synthesizing of its single crystal free of surface defects is a pressing matter of the moment. In this paper, the key points in preparing such single crystal are concluded, that is high vacuum, long time, and small ΔT, sometimes the transport agents have to be used to help the matter diffusion. And the proper quantities of these parameters are detailed in this paper too.

Sensitive Planar Microwave Diode on the Base of Ternary AlxGa1-xAs Semiconductor Compound

The article presents the results of experimental studies of the dc and high-frequency electrical characteristics of planar microwave diodes that are fabricated on the base of the n-AlxGa1-xAs layer (x = 0, 0.15 or 0.3), epitaxially grown on a semi-insulating GaAs substrate. The diodes can serve as reliable and inexpensive sensors of microwave radiation in the millimeter wavelength range; they sense electromagnetic radiation directly, without any external bias voltage at room temperature. The investigation revealed a strong dependence of the detection properties of the microwave diodes on AlAs mole fraction x: in the Ka microwave frequency range, the median value of voltage responsivity is several volts per watt in the case of GaAs-based diodes (x = 0), and it substantially increases, reaching hundreds of volts per watt at higher x values. Also, a model enabling us to forecast the responsivity of the sensor in other frequency ranges is proposed.