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

本文用反射高能电子衍射（RHEED）、扫描电子显微镜（SEM）和扫描俄歇微探针（SAM）研究了在覆盖有氟化钙（CaF_2）绝缘膜的硅（111）衬底上外延生长硅薄膜。CaF_2薄膜是在Si（111）7 × 7表面上于600 ℃以反平行于衬底晶体取向外延生长的。本文提出了一种在Si（111）-CaF_2上生长硅薄膜的两步生长法：先在室温下沉积少量双层硅，然后将样品加热到600 ℃，使生长的硅薄膜具有良好的结晶性。生长的硅晶体膜的取向平行于CaF_2晶体，反平行于衬底硅晶体。用RHEED探针在室温下对CaF_2表面进行电子束辐照，可以使生长的硅膜更加均匀，并抑制了硅与CaF_2表面的反应性。 关于我们 然而，生长的硅膜的表面没有表现出清洁的Si（111）表面的7 × 7结构，而是由于在表面上存在少量的钙而表现出1 × 1结构。从SAM深度剖面测量中发现，在室温下，用500 eV氩离子溅射，掠射角为30 °时，可以除去表面的钙吸附物，并且杂质元素没有掺入生长的硅膜中。另一方面，初步的退火实验表明，在1000 ℃退火后，生长的硅膜表面出现了与硅衬底晶体反平行取向的7 × 7结构，而绝缘CaF_2膜变薄并局部消失。这些结果表明，采用电子束辐照CaF_2表面，采用两阶段生长法，再结合掠入射低能离子溅射和适度退火，可以获得表面清洁的硅薄膜。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