Time-Resolved Observation of Laser-Induced Surface Reaction for Si/Cl2 System Using Second-Harmonic Generation

Abstract

Laser-induced surface reaction for the Si(111)/Cl2 system has been observed using second-harmonic generation (SHG). Chlorine gas molecules are introduced to the clean Si surface and their adsorption, desorption and reaction are indirectly measured by surface SHG. In the case of Nd:YAG laser measurement, SHG output decays rapidly with exposure to Cl2 and is recovered by pump beam irradiation with a power of 65 mJ/pulse. Cl coverage can be estimated from SHG intensity and we determine the mean residence times of adsorbed Cl to be 300 ns and 11.4 s with and without pump beam exposure, respectively, at a sample temperature of 180° C. In the case of Ti-sapphire laser measurement, SHG outputs increase and decay rapidly with exposure to Cl2 as measured by 800 nm and 1300 nm probe beams, respectively.