Catalytic Reactions in Crystal Growth and Etching Processes at Semiconductor Surfaces: First-principles Molecular Dynamics Study

活动时间： 05月18日09时00分       

地            点  ： 理科楼2-B409

讲座内容：

In this talk, two topics will be discussed: the first one is on the promotion mechanism of GaN single crystal growth in the Na flux method. The Na flux method is one of very promising techniques to grow large GaN single crystals with high quality. The solubility of N into liquid Ga is quite low and therefore very severe conditions such as high pressure of 1 GPa and high temperature of 1773K are necessary to grow GaN crystals. On the other hand, the solubility of N into Ga-Na liquid alloy is significantly higher and the required pressure and temperature can be reduced to 2-3 MPa and 1023K. First-principles molecular dynamics simulations have been carried out to clarify the microscopic origin for the enhancement of N dissolution and the growth of GaN single crystals by Na. The second topic is the catalytic reactions in etching processes at SiC single crystal surfaces. SiC and GaN are quite stable semiconductors and therefore, it is rather difficult to etch surfaces of these materials. Recently, Yamauchi and co-workers in Osaka University group proposed a quite promising etching method to produce atomically flat SiC and GaN surfaces using Pt plate as a catalyst and they named the method “catalyst-referred etching (CARE)”. In the CARE method, SiC surfaces are etched in HF solutions with a Pt plate and they suggested that etching reactions take place at the contact region between the SiC surface and the Pt catalyst. Density functional theoretical simulations have been carried out to clarify the reaction mechanisms.

主讲人介绍：

Prof. Yoshitada Morikawa received his B.Sc. and M.Sc. degrees in KyotoUniversity in 1989 and 1991, respectively; and Ph.D. degree in the University of Tokyo in 1994. From 1994 to 1995, he worked in KyotoUniversity as the JSPS Fellow. After that, he worked in JRCAT, NAIR, JAIST, RICS, and AIST as a research scientistsuccessively. He has devoted himself to the development of STATE code. He visited Technical University of Denmark as a visiting associate professor at the years of 2003 and 2004. He began to work in OsakaUniversity from 2004, and became the professor in 2009. His current interests include first-principles simulations of surfaces and interfaces, heterogeneous catalysts, electrochemistry, inorganic and organic semiconductor interfaces. Prof. Morikawa has published 131 peer-review journal papers with a total citation of 4776 and h-index of 37.

发布时间：2017-05-11 09:02:40