Abstract

Optical second-harmonic generation (SHG) is a surface sensitive probe from which adsorbate coverage, bonding site, and orientation have been deduced.¹ Surface symmetry may also be probed with SHG.² Here we discuss the use of SHG to study the time evolution of dynamic processes on surfaces. At typical gas-surface reaction time scales of 1 s we have been able to follow the room temperature chemisorption of oxygen on Si(111)–7X7. We find that the dangling bonds and 3m arrangement of the Si backbonds are depleted at a rate of (3.5 × 10⁻⁶Torrs)⁻¹ while full oxidation of the Si backbonds proceeds at a slower rate of (35 × 10⁻⁶ Torrs)⁻¹. A far more unique use of SHG, however, is to use SHG to study the surface dynamics induced by an intense laser pump pulse. Such measurements have time resolution limited only by the laser pulse width. We report recent work on laser-induced disorder/melting of Si (111) and Cu(111) single crystals with 100-fs time resolution.

© 1986 Optical Society of America