用高能量電子繞射及掃描穿隧電子顯微術探討分子術磊晶的Mg/MgO(110)介面與Mg的皺化

• Main Author: 柯佳均
• Other Authors: 陳恭
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/92334194354879720708

碩士 === 國立中正大學 === 物理系 === 88 === We grow Mg/MgO(110) by MBE and use in situ reflection high electron diffraction (RHEED) to measure the original stage of the growth and then use scanning tunneling microscope (STM) to obtain the surface images until the film gets thicker. We get a clear picture of the interface structure and the surface morphologies of the present metal/oxide system. The observation in this study is: the initial stage for Mg films grow on MgO(110) is pesudomorphic because of the cohesive energy is weaker between Mg-Mg then Mg-MgO. Mg films soon transfer, after the thickness greater than 12Å(5-6 ML), to relax to it’s stable bulk structure. When the thickness reach 16Å, there are new points show out in the RHEED pattern. The crystal structure start to change on this moment. There are no high symmetry planes in a hcp structure assemble fcc(110) planes. The closely match low symmetry planes in hcp structure have a (6×1) symmetry in plane. After the thickness greater than 64Å,the new points become brighter and there are lines connect with points. It shows there are facets and the shape is triangular long islands. We get the same result from the STM image. The planes of the facets are fcc(111) and enlarge along the [110] direction. The RHEED pattern show the “ V ” shape at the same time and have image symmetry by the center line of the pattern. We assume there are twin form in the facet. When the thickness is 208Å. The original center point become dark, maybe it’s the critical thickness to change to stable hcp structure. The situation keep after 300Å Mg is deposited. For STM study, there are 18 triangular islands in 500×500 nm2 area. The wide and high of the islands are 64.01Å and 23.99Å by statistical,and the angle is 37°,it’s very close to the theoretical value-35°. The serrature surface morphology are observed in the facet plane, it shows the plane of fcc(111) is very rough. Besides this, there are large difference in surface morphology when the orientation of MgO substrate are different. On MgO(100), hexagonal shape terraces are observed. On MgO(111), Mg film is relatively flat but with some unexpected nano-scaled facet. It’s clear that the surface morphology and grow mode are determined by the original MgO orientations.