SEM images of (a) Si NWs and (b) Ge NWs grown on a Si(111) surface by MBE. The orientations of the NWs are indicated in the SEM images. The growth times were 2 and 1 h for the Si and Ge NWs, respectively. The scale bars correspond to 400 nm.
Xu et al. Nanoscale Research Letters 2011 6:113 doi:10.1186/1556-276X-6-113