High-Resolution Electron Microscopy Studies of Surface Structures and Reactions

High-resolution electron microscopy(HREM) has been used to study crystal surfaces, especially the surfaces of compound semiconductor materials, with the microscope configurations of profile imaging and reflection(REM). For profile imaging, studies with multislice simulations have been made to investigate the possibilities of imaging real surfaces with defects, relaxations, reconstructions and so on. The technique has also been applied in practice to study the reconstructions and dynamics on the surfaces of compound semiconductors, in particular the various reconstructions and atomic rearrangements on the CdTe surfaces. The electron -beam-induced oxidation on the surfaces of CdTe, ZnTe and InP has been investigated. The oxidation processes and products under different experimental conditions such as electron beam current density, electron beam energy, as well as vacuum pressure inside the microscope column have been investigated and compared with those resulting from thermal oxidation experiments in air. In the reflection geometry, electron scattering processes on GaAs surfaces have been studied with multislice simulations and reflection electron energy loss spectroscopy(REELS) experiments, and a variation of electron channelling behaviour on the surfaces under different diffraction conditions has been found. These results were used to characterize the surfaces, such as the determination of surface termination of GaAs(100).