Growth of Silicon Thin Film on Si (111)-CaF_2 for the Measurement of Surface Electronic Properties

点击翻译按钮获取中文摘要

Epitaxial growth of silicon thin crystal film on silicon (111) substrate which had been covered with calcium fluoride (CaF_2) insulator film has been studied by RHEED (Reflection High Energy Electron Diffraction), SEM (Scanning Electron Microscopy) and SAM (Scanning Auger Microprobe). CaF_2 film is grown epitaxially on Si (111) 7x7 surface at 600ﾟC in antiparallel orientation to the substrate crystral. Two-stage growth method has been developed to grow a silicon thin crystal film on the Si (111)-CaF_2 : A few bilayrs of silicon were deposited initially at room temperature and then the specimen was heated up to 600ﾟC for the growing silicon film to have good crystallinity. The orientation of growing silicon crystal film is parallel to CaF_2 crystal and antiparallel to the substrate silicon crystal. It was found that electron beam irradiation of CaF_2 surface using the RHEED probe at room temperature made the growing silicon film more uniform and suppress the reactivity between silicon a … More nd CaF_2 at 600ﾟC.However, the surface of the growing silicon film did not exhibit the 7x7 structure of the clean Si (111) surface, but the 1x1 structure due to the presence of a small amount of calcium on the surface. It was found from the depth profile measurement using SAM that calcium adsorbates can be removed from the surface by 500eV Ar ion sputtering with glancing angle of 30ﾟ at room temperature and the impurity elements were not incorporated in the growing silicon film. On the other hand, it was shown by preliminary annealing experiments that the 7x7 structure appeared on the surface of the growing silicon film in antiparallel orientation to the silicon substrate crystal after annealing at 1000ﾟC,while the insulating CaF_2 film was thinned and disappered locally. These results strongly suggest that silicon thin films with clean surfaces can be obtained using the electron beam irradiation of CaF_2 surface and the two-stage growth method followed by low-energy ion sputtering with grazing incidence and moderate annealing. Less