AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS3+EM-WeM

Paper SS3+EM-WeM1
Spectroscopic Nonlinear Optical Responses of Clean, H-terminated and Ge-covered (2x1)Si(001)

Wednesday, October 27, 1999, 8:20 am, Room 604

Session: Surface Electronic Structure
Presenter: L. Mantese, University of Texas, Austin
Authors: L. Mantese, University of Texas, Austin
D. Lim, University of Texas, Austin
M.C. Downer, University of Texas, Austin
Correspondent: Click to Email
Nonlinear optical spectroscopies are becoming important in elucidating the electronic structures of surfaces and interfaces. Yet, the accurate theoretical calculation of these spectra remains a difficult challenge. Recently, theoretical models have been developed to predict the nonlinear optical responses of clean and absorbate-covered (2x1)Si(001) surfaces.@footnote 1,2@ Here, we report the second harmonic (SH) responses of clean, H-terminated and Ge-covered (2x1)Si(001) to provide a direct test of predictive models. We have extended the range of previously reported results@footnote 3,4@ further into the IR where tunable IR femtosecond pulses in the range of ~1.15 to 2.5 microns were generated by a commercially available optical parametric amplifier (OPA) system. In this excitation region the SH response is resonantly enhanced by surface states including those from the dangling bonds and reconstruction-induced bonds. In addition, by directly using our oscillator output (700 to 800nm), we measure nonlinear optical responses in the E@sub 1@ region of Si. In this spectral range the SH response is highly sensitive and is altered in contrasting ways to ML coverages of H and Ge on (2x1)Si, originating from a surface electric field related to dimer charge transfer. The two measurement regions are discussed in comparison with theoretical predictions. @FootnoteText@ @footnote 1@B. Mendoza et al., PRL 81 (1998) 3781. @footnote 2@V.I. Gavrilenko et al., PRL submitted (1999). @footnote 3@U. Hofer, Appl. Phys. A 63 (1996) 533;J.I. Dadap et al., PRB 56 (1997) 13367. @footnote 4@P. Parkinson et al., Appl. Phys. B 68 (1999) 1.