Study of Atom Dynamics and Surface Conductance during Epitaxial Growth

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We have studied surface structures, surface composition and surface conductivity during epitaxy by RHEED (Reflection High Energy Electron Diffraction), TRAXS (Total Reflection Angle X-ray Spectroscopy). RHEED is powerfull for structure analysis through reciprocal lattice and STM (Scanning Tunneling Microscopy) is powerfull for obsrvation of the lattice images in the real space. Thus, this project is to study the epitaxial phenomenon by using a combined apparatus of RHEED-TRAXS and STM.In 1994, we obtained a STM observation head and constructed a instrument which can approach slowly to the sample surface and a scanning system. In 1995, we obtained a low voltage power supply, a picture processing system and a probe scanning circuit and complated as a system which can observe RHEED patterns and STM images.Using the apparatus, we studied clean Si (111) surface structure and reconstructed surface structures which were formed by In deposition on Si (111) surface. STM images of the clean surface showing a clear 7X7 RHEED pattern showed partly no 7X7 contrast in the STM images. It is thought that some gases may adsorbed on the 7X7 surface during cooling. If the 7X7 structure is not destroy by the gas adsorption, a clear RHEED pattern would be observed. However, STM image may be affected very much even at slight gas adsorption. Next, we observed 1X1,4X1, @6931X@6931, @693X@693 structures when In was deposited on a Si (111) surface. We studied these structures in details by STM and analyzed. We proposed new surface structure models for such reconstructed surface structures. Besides, we measured the surface conductivity during the epitaxial processes.