Real-space observation of (111) facet formation on vicinal Si(111) surfaces

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Abstract
We report real-space observations of nucleation of (111) facets with 7×7 structures on a vicinal Si(111) surface using ultrahigh-vacuum scanning electron microscopy. As reported previously by Phaneuf et al., who used low-energy electron microscopy [Phys. Rev. Lett. 67, 2986 (1991)], (111) facets grow in very anisotropic shapes and are much longer along steps than normal to steps. In addition, we show that (1) the facet width is dependent on the heating current direction and (2) the facets tend to nucleate adjacent to one another. The second result is explained by the fact that stepped regions near the facets are not uniformly inclined but undulated. The local inclination is directly observed using ex situ atomic force microscopy and is in good agreement with calculated results accounting for step-motion kinetics. Additionally, we link the disappearance of the (111) facets to As adsorption.