Electronic structures of Si(1 1 1) in the 7 7 $ ``1 1ʹʹ phase transition studied by surface second-harmonic generation

Surface second-harmonic generation (SHG) of Si(1 1 1)-7 7 shows an increase in intensity for the surface-state transition (56%) and the strain-induced E00 interband transition (32%) in response to the phase transition to ``1 1ʹʹ taking place around 1100 K. The SHG surface-state transition in ``1 1ʹʹ is assigned as the redshifted S3 ! U1 transition in 7 7 from the observation of no discernible changes in the resonant characteristics. From the symmetry and atomic geometry of the electronic states responsible for SHG, the intensity jump is related to the dissolution of the stacking fault in the ``1 1ʹʹ phase. # 2001 Elsevier Science B.V. All rights reserved.