Figure 3 .
SEM images of the GaN nanowires. Grown on the c-plane GaN substrate with the Ga source placed at various distances to the substrate. The distances were (a) and (b) 15 cm, (c) and (d) 20 cm, and (e) and (f) 25 cm.
Hou et al. Nanoscale Research Letters 2012 7:373 doi:10.1186/1556-276X-7-373