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（RHEED）、扫描电子显微镜（SEM）和扫描俄歇探针（SAM）研究了氟化钙（CaF_2）绝缘体膜覆盖的硅（111）衬底上硅薄膜的外延生长。在600℃的温度下，在Si (111) 7x7表面沿与衬底晶体反平行的方向生长CaF_2薄膜。采用两段生长法在Si (111)-CaF_2上生长硅薄膜：在室温下先沉积几层双层硅，然后加热至600℃，使生长的硅薄膜具有良好的结晶度。生长硅晶体薄膜的方向与CaF_2晶体平行，与衬底硅晶体反平行。结果表明，在室温下，用RHEED探针对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600℃时CaF_2与硅之间的反应性。然而，生长中的硅膜表面并没有呈现出干净Si（111）表面的7x7结构，而是由于表面存在少量的钙而呈现出1x1结构。利用SAM进行深度剖面测量发现，在室温下，以30‰的扫射角溅射500eV的氩离子，可以去除表面的钙吸附物，并且杂质元素没有掺入生长的硅膜中。另一方面，初步退火实验表明，在1000℃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，而绝缘的CaF_2膜则变薄并局部消失。这些结果表明，采用电子束辐照CaF_2表面，再经过低能离子溅射和适度退火的两阶段生长方法，可以得到表面干净的硅薄膜。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