Optical second harmonic spectroscopy of the Si(001) E/sub 1/ critical point resonance with variable hydrogen coverage

Summary form only given. A number of recent second harmonic (SH) spectroscopic studies of Si-SiO/sub 2/ interfaces and clean reconstructed Si surfaces have reported interfacial E/sub 1/ critical point two-photon resonances at energies (3.2 to 3.3 eV) that are strongly redshifted from the bulk E/sub 1/ energy (3.37 to 3.40 eV). Although these red shifts have been qualitatively interpreted exclusively in terms of subsurface tensile strain, the shifts are larger than known microscopic models of vertical Si-Si bond stretching near the interface can explain. In the current work we track the magnitude, of the resonance as expected with relaxation of subsurface strain, which enhances the second-order susceptibility component; however, the peak red shifts away from the bulk E/sub 1/ energy.