Core-shell SiGe whiskers with composition gradient along the axial direction: Cross-sectional analysis

Abstract
Core-shell SiGe whiskers were grown via a fully self-organized process without artificial control of source materials. Whiskers were several hundred nanometers in diameter at the top and became thicker towards the bottom, and 100μm long. Cross-sectional observations of a whisker clearly showed that the whisker had core-shell structure: both the core and the shell were SiGe and the core was Ge-richer in comparison to the shell. It was also elucidated that the whisker had composition gradient along the axial direction. It was concluded that core and the shell were formed via vapor-liquid-solid and vapor-solid processes, respectively.