Study of Si(111) surfaces by optical second-harmonic generation: Reconstruction and surface phase transformation.
Optical second-harmonic generation has been applied to the study of clean Si(111) 2\ifmmode\times\else\texttimes\fi{}1 and 7\ifmmode\times\else\texttimes\fi{}7 surfaces. By an analysis of polarization dependences of the two reconstructions, the symmetry properties of the surfaces have been determined. The 2\ifmmode\times\else\texttimes\fi{}1 to 7\ifmmode\times\else\texttimes\fi{}7 surface phase transformation during thermal annealing has also been monitored in real time by the second-harmonic technique.