Heat treatment temperature effects on the formation of Mg2Si films deposited by electron beam evaporation

It is of great importance to do research on the preparation and applications of the Mg2Si film as an ecological friendly semiconducting material. Semiconducting Mg2Si films were prepared by electron beam evaporation deposition of Mg film onto Si substrate and subsequent heat treatment. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize and analyse the obtained Mg2Si films. Effects of heat treatment temperature (300-700 degrees C) under Ar gas pressure (200 Pa) on the crystal structure and surface morphologies of Mg2Si films were investigated. The XRD results show that heat treatment at 400-500 degrees C for 4-5 h is the optimal heat treatment condition to prepare Mg2Si films by the diffusion between the Mg atoms and Si atoms, and high temperature treatment above 600 degrees C causes the decomposition of Mg2Si and the formation of MgO. The SEM images show that the surfaces of obtained films become smooth and compact with the increase in heat treatment temperature. However, significant differences on the surface of the films occur when heat temperature is above 600 degrees C because of the decomposition of Mg2Si phase and the formation of MgO phase. These experimental results are beneficial to the development of optoelectronic devices based on the Mg2Si films.