Control of the heteroepitaxal growth on vicinal surfaces

Research Project

Project/Area Number	11555188
Research Category	Grant-in-Aid for Scientific Research (B).
Allocation Type	Single-year Grants
Section	展開研究
Research Field	Material processing/treatments
Research Institution	Waseda University
Principal Investigator	OSAKA Toshiaki Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (50112991)
Project Period (FY)	1999 – 2000
Project Status	Completed (Fiscal Year 2000)
Budget Amount *help	¥6,300,000 (Direct Cost: ¥6,300,000) Fiscal Year 2000: ¥2,800,000 (Direct Cost: ¥2,800,000) Fiscal Year 1999: ¥3,500,000 (Direct Cost: ¥3,500,000)
Keywords	Si(111) / vicinal surface / controlling growth morphology / critical film thickness / strain relaxation / surface step / 微傾斜基板 / Sn薄膜 / 成長形態制御 / Keatingポテンシャル / 弾性歪みエネルギー
Research Abstract	In this study, we aimed (i) to prepare a vicinal surface on the Si(111) substrate, (ii) to grow a diamond type of Sn (α-Sn) on the surface, which is the same IV group to Si and is in a large lattice-mismatched relationship with it, and (iii) to control stably its growth morphology. Prior to our experiments, firstly, elastic-strain energy stored at the interface of α-Sn/Si(111) was calculated theoretically using the Keating potential. This calculation gave us the important suggestion that steps on the Si(111) vicinal surface may relax effectively strain energy in the growing film and allow to grow pseudomorphologically α-Sn beyond a critical thickness. On the basis of this result, secondly, we actually grew α-Sn on the 6゜ -inclined vicinal surface, and assessed its process by using reflection high-energy electron diffraction (RHEED) and scanning turneling microscopy (STM). These results are as follows : RHEED patterns showed that terraces on the vicinal substrate used are inclined against the direction normal to the substrate surface and their widths are very narrow. From the STM observation, we gained information of linearity in the step line and nonuniformity in the terrace. Depositing Sn on such vicinal surfaces, we recognized the formation of an adsorption structure having a √3×√3 -R30゜ period. Then, excess Sn forms an α phase, leading to the formation of a facet inclined 19.5゜ form the [11-2] direction of Si(111). Although further growth of Sn causes a phase change from α to β, finally, the whole film becomes α-Sn, presumably stimming from an origin of soft elasticity of Sn. The results show that the utilization of a vicinal surface enables us to control stably the morphology of epitaxicially grown films in the large lattice-mismatched systems.