The Growth Morphology of MgO on Si(111) and Graphite

• Main Authors: Jhih-Yi Liang, 梁志繹
• Other Authors: Fu-Kwo Men
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/85136094826712966412

碩士 === 國立中正大學 === 物理學系暨研究所 === 101 === By growing MgO thin film on a semiconductor substrate and then growing ferromagnetic/non-magnetic metal multilayers on the MgO film, literature has reported that the ferromagnetic metal film shows perpendicular magnetic anisotropy, indicating the MgO film plays a crucial role in the perpendicular anisotropy. In our experiment, Si(111) and highly oriented pyrolytic graphite (HOPG) substrates have been used to grow MgO film. Scanning tunneling microscopy and atomic force microscopy, respectively in vacuum and under atmospheric pressure, were employed to observe surface morphology. Our observations show that, by growing MgO on a Si(111)-(7×7) surface, randomly distributed MgO clusters coalesce to form elongated chain structure in a direction parallel to the surface step after heating the MgO-deposited surface. For MgO growing on a HOPG surface at room temperature, we have found that the MgO clusters distribute rather unevenly on the surface. Most MgO clusters tend to grow along the step edges, leaving terraces virtually free of clusters. The MgO clusters coalesce and large clusters emerge after heating, an indication of Ostwald ripening at work. We have intentionally placed a MgO-grown HOPG surface in the atmosphere for extended period of time. After 24 hours, uniformly distributed MgO clusters show up on the surface. Regularly shaped clusters, i.e., crystalline MgO clusters, emerge after 48 hours of exposing in the atmosphere. Though growing on two drastically different substrates, the kinetics of MgO growth appears to show a similar pattern: clustering followed by coalescence into elongated chain structure.