| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuP |
| Session: | Thin Films Poster Session |
| Presenter: | Akitaka Yoshigoe, Japan Atom Energy Agency, Japan |
| Authors: | A. Yoshigoe, Japan Atom Energy Agency, Japan R. Okada, University of Tsukuba, Japan Y. Teraoka, Japan Atomic Energy Agency, Japan Y. Yamada, University of Tsukuba, Japan M. Sasaki, University og Tsukuba, Japan |
| Correspondent: | Click to Email |
Germanium (Ge) has been interesting as future substitute channel material for metal-insulator-semiconductor field-effect-transistors (MISFETs) because of its high carrier mobility. Although precise controlling of the surface oxide layer of Ge surfaces is important for fabrication of dielectric/Ge interface in Ge-based devices, fundamental aspects of oxidation reaction at Ge single crystal surfaces and nature of the oxide monolayer have not yet been well understood. In this presentation, we report the nature of oxides of Ge(100)-2×1 and Ge(111)-c(2×8) surfaces fabricated with pure oxygen gas (O2) at 300 K. Surface oxide and its evolution from very initial stages to the maximum oxide coverage were measured by real-time photoelectron spectroscopy using synchrotron radiation. All experiments were conducted with SUREAC2000 at BL23SU in Spring-8. We found the saturation oxide coverage on both surfaces is less than one monolayer. We found that initial sticking coefficient of O2 was much smaller than that for Si(100). SR-XPS measurements demonstrated that the maximum oxidation number of Ge in saturation region was as small as 2+, which exhibits a strong contrast to the case of Si where 4+ state is spontaneously formed. Our results suggest that native oxides layer with Ge4+ cannot be formed only with pure O2 gas. Our findings reveal the significant difference between the nature of surface oxides of Ge and Si and can be useful for a precise control of oxide layer on Ge surfaces.
This research was partially supported by grants-in-aid from the Ministry of Education, Cultures, Sports, Science and Technology, for Exploratory Research, No. 26420289. The synchrotron radiation experiments were performed at the BL23SU of Spring-8 with the approval of JASRI (Proposal No. 2007B3802, 2008A3804, 2008B3804, 2009A3804, 2011A3804, 2011B3802, 2012A3802, 2012B3802, 2013A3802, and 2013B3802).