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

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. The author shows that optical second-harmonic generation can be used successfully to probe this structure for metal-silicon systems. Second-harmonic studies of Si(111)-Au and Si(100)-Au have been carried out in a conventional ultra-high vacuum system equipped with low-energy electron diffraction and Auger electron spectroscopy. A strong second-harmonic signal is obtained which is shown to originate at the buried interface and to persist through at least 30 AA of deposited gold.