Dependency of a localized phonon mode intensity on compositional cluster size in SiGe alloys
Sylvia Yuk Yee Chung,
Motohiro Tomita,
Junya Takizawa,
Ryo Yokogawa,
Atsushi Ogura,
Haidong Wang,
Takanobu Watanabe
Affiliations
Sylvia Yuk Yee Chung
Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan
Motohiro Tomita
Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan
Junya Takizawa
Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan
Ryo Yokogawa
School of Science and Technology, Meiji University, Kawasaki 214-8571, Japan
Atsushi Ogura
School of Science and Technology, Meiji University, Kawasaki 214-8571, Japan
Haidong Wang
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
Takanobu Watanabe
Faculty of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan
Using molecular dynamics, we found that the localized phonon-mode spectrum in SiGe alloys, which was recently discovered by an inelastic x-ray scattering experiment, changes according to the size distribution of compositional clusters in alloys. By varying the spatial distributions of Si and Ge, alloy models with differing compositions of Si and Ge clusters were able to be produced. For a range of alloys comprising 20%–80% Ge, a mixture of small and intermediate sized clusters will give the highest intensities of the local mode. The Si–Ge optical mode intensity increases with the local mode intensity, but the Si–Ge bond alone is not sufficient to produce the local mode. Si rich alloys with small Ge clusters produce the highest local mode intensities, suggesting that this mode is caused by small Ge clusters surrounded by Si pairs.
