Real-Time Observation of (1×1)-(7×7) Phase Transition on Vicinal Si(111) Surfaces by Scanning Tunneling Microscopy

Scanning tunneling microscopy of a Si(111) surface with a misorientation of 10° reveals that the (7×7) domains form stripes whose widths are quantized in units of a (7×7) unit cell. The (7×7)-to-(1×1) phase transition on this surface occurs at about 1030 K when the temperature is increased, which is about 80 K lower than that for a nominally flat Si(111) surface, and the (1×1)-to-(7×7) phase transition occurs at 1003 K when the temperature is reduced. Nucleation and growth of (7×7) domains are explained in terms of the domains' energy gain and the energy loss of the domain edges and slant surfaces.