Determining metal–semiconductor interface structure by optical second-harmonic generation

Abstract

Conventional surface science techniques provide little information about the structure of the buried metal–semiconductor interface, where many layers of metal have been deposited on the semiconductor surface. We show that optical second-harmonic generation (SHG) can be used successfully to probe this structure for metal–silicon systems. SHG studies of Si(111)–Au and Si(100)–Au have been carried out in a conventional ultrahigh vacuum system equipped with low-energy electron diffraction and Auger electron spectroscopy. A strong SHG signal is obtained which is shown to originate at the buried interface and to persist through at least 30 Å of gold.