Anisotropic etching induced by surface energy driven agglomeration

The authors report on a previously unobserved anisotropic etching method in which a eutectic droplet created by heating a multilayer Au/Ge film is driven to form negative pits on the crystalline semiconductor surface. The etching process involves surface diffusion, evaporation, and pit formation. The shape of the pit is controlled by the underlying substrate symmetry. The surface morphology, crystal structure, and interfacial composition of the substrate (Si and Ge) were studied as a function of the thickness of the Au and Ge bilayer using scanning electron microscopy. The placement and size of the negative pits can be controlled by prepatterning the film.