The Study Of Hgte Crystal(111)Surface And HgTe/CdTe/GaAs Films By STM

Mercury telluride has drawn great attention for its intriguing properties and tremendous application potentials,especially for those related to the topological electronic structures.Howevere,so far the investigations of HgTe surface structure by scanning tunneling microscopy(STM)are rarely reported,especially for HgTe(111)surface.The main experimental results are listed below:(1)HgTe(111)surface is comprehensively studied by scanning tunneling microscopy(STM)/ spectroscopy(STS).Besides the primitive(7)1 ?1(8)hexagonal lattice,six reconstructed surface structures have been observed:(2×2),“2×1”,“4×1”,“3×?3”,“2?2×2” and “?11 ×2”.The(2×2)reconstructed lattice maintains the primitive hexagonal symmetry,while the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the “3×?3” reconstruction are bias dependent,indicating they have both topographic and electronic origins.There are mainly two reasons for the reconstructions observed here: one is the large stress induced by the mechanical cleavage;the other is the desorption of Hg atoms due to its high vapor pressure.The STSs obtained at different reconstructed surfaces show a universal dip feature with size ~100 mV,which may be attributed to the surface distortion.(2)High quality HgTe films are deposited on the CdTe/GaAs substrates by molecular beam epitaxy,and characterized by reflection high-energy electron diffraction,X ray diffraction,scanning electron microscopy and scanning tunneling microscopy,the scanning tunneling microscopy topographys show that the smoothness and conductivity of HgTe(111)surface become better after Ar etching and annealing,and the fluctuation of surface keep in a few nanometers.