Characterisation of Au films on Si(1 1 1) 3×3-Au by photoemission and optical second-harmonic generation

Synchrotron radiation photoemission in combination with optical second-harmonic generation (SHG) is used to study the growth of thin Au films on the 3×3-Au-reconstructed Si(1 1 1) surface. The Si2p and Au4f core level spectra show the formation of a surface compound that has stabilized to a constant level at 5-monolayer coverage. Valence band spectra show thickness-dependent structures interpreted as quantization effects in the direction perpendicular to the surface. This is supported by optical SHG experiments showing oscillations in the signal with film thickness due to the shift of the quantized levels. The oscillating second-harmonic signal depends on the azimuthal sample orientation and thus originates from a film with crystalline order. From the thickness dependence of the second-harmonic signal in combination with the photoemission results it is concluded that the Au film is well-ordered below a thin reacted surface layer.