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

用反射高能电子衍射仪(RHEED)、扫描电子显微镜(SEM)和扫描俄歇探针(SAM)研究了外延生长已被CaF_2绝缘膜覆盖的硅(111)衬底上的硅薄膜。在600ﾟC的温度下，在Si(111)7×7表面上外延生长了与衬底晶体相反的CaF_2薄膜。采用两步生长法在Si(111)-CaF_2衬底上生长硅薄膜：首先在室温下沉积几层硅，然后将样品加热到600ﾟC，以使生长的硅膜具有良好的结晶度。生长的硅单晶膜的取向为平行于CaF_2晶体，反平行于衬底硅晶体。结果表明，在室温下用RHEED探头对CaF_2表面进行电子束辐照使生长的硅膜更加均匀，并抑制了硅与…之间的反应活性当温度为600ﾟ时，生长的硅膜表面呈现出1x1结构，而不是纯净的Si(111)表面的7x7结构，这是由于表面存在少量的钙。用扫描电子显微镜测量深度分布发现，在室温下，用500 eV的Ar离子溅射，掠射角为30ﾟ时，表面上的钙吸附物可以被去除，而且生长的硅膜中没有杂质元素。另一方面，初步的退火实验表明，在1000ﾟC下退火后，生长的硅膜表面出现了与硅衬底晶体反平行的7x7结构，而绝缘CaF_2膜局部变薄和消失。这些结果有力地表明，用电子束辐照CaF_2表面，然后用低能离子溅射、掠入射和适度退火的两步生长方法可以获得表面清洁的硅薄膜。较少

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