Stability of the Si-H bonds on the hydrogen-terminated Si(111) surface has been investigated by sum frequency generation (SFG) spectroscopy in air at room temperature. The SFG observation showed that the Si(111) surface is terminated by a monolayer of monohydride (Si-H) after etching in a concertrated ammonium fluoride (NH4F) solution. The number of Si-H bonds decreased with laser irradiation time and the abstraction rate of hydrogen atoms on Si increased with the increase of input energy of "visible" light. The Si-H bond under irradiation at 1064nm light was more stable than that at 532nm light with a given intensity. A small amount of water in air severely lowered the stability of Si-H bond because of a photoelectrochemical recation under laser irradiation. 表面和頻光譜分析系統(tǒng)(SFG) PL2230系列高能量全固態(tài)鎖模皮秒Nd:YAG激光器