Atomic-Scale Effects of Applied Strain on Etching of Si(100)

An ideal hydrogen-terminated Si(100) surface would be highly stressed due to unfavorable steric interactions between neighboring surface sites (i.e. neighboring silicon dihydride species). As a result, some aqueous etchants selectively remove every other silicon dihydride to relieve the stress, producing an unusual striped morphology. In these experiments, we apply a uniaxial strain to the surface during etching. Using a combination of scanning tunneling microscopy and surface infrared spectroscopy, we show that applied strains dramatically alter the etch morphology and the surface species, in some cases promoting the formation of hillocks. These effects are explained in terms of the site-specific reactivity of the etching silicon surface.