Surface reconstruction and crystal structure of MgSe films grown on ZnTe substrates by MBE

摘要

MgSe is an important component in Mg-based ternary or quaternary alloys, but is less understood due to its hygroscopy and unstable zinc blende structure. In order to get a clear knowledge of this material, we have investigated the growth of MgSe films of ZB,(zinc blende), structure on ZnTe substrates by MBE (molecular beam epitaxy). The surface reconstruction of MgSe under different flux ratios and growth temperatures have been studied systematically by RHEED (reflected high-energy electron diffraction). (4 x 1) reconstruction is observed under Ⅵ/Ⅱ flux ratios of 16-30, while (2 x 1) reconstruction appears at higher Ⅵ/Ⅱ ratios. The oscillation of RHEED intensity at the first stage of MgSe growth indicated that 2D growth was achieved, and thereafter the growth mode changed to 3D growth due to the lattice mismatch. The structure of the MgSe layer is further confirmed by XRD (X-ray diffraction). The XRD results indicated the growth of a MgSe film having a ZB structure for a layer below 2000 A thick. No diffraction is observed from 2000 to 4000 A thick MgSe films. Thicker samples show the formation of MgSe layers having a rock salt structure.