Figure 1.

Microscopy images. (a) Optical image of porous silicon microspheres, and (b) optical image of a:Si-H microspheres. While porous silicon microspheres scatter yellow, orange, and red colors when irradiated by white light, a:Si-H microspheres look like black due to the absorption of visible light by silicon. (c) SEM image of a porous silicon microsphere of about 2 μm in diameter (reprinted with the permission of [12]).