Effect of Laser Irradiation on Oxygen Defect Concentration on Disperse Si02 Surface

The analysis of spectral luminescence characteristics of disperse Si02 indicates the presence of two types of surface oxygen vacancies (O-VI and O-VII). Their concentrations can be decreased by means of near UV and IR laser irradiation. It is established that the O-V concentration decreasing under IR irradiation (λirr = 1064 nm) in air is caused by their laser annealing under seven-photon ionization of surface O-V with the participation of atomic oxygen formed near the surface under dissociation of atmospheric 02 molecules in the laser field. The irradiation by near UV laser light (λirr ~250-360 nm) leads to a lower effective O-V concentration with decreasing IR irradiation. The analysis of the dose dependence shows that in this case the observed effect is due to the interaction of surface O-V with bulk reagents (water, OH− groups, 02 centers) or their photolysis products, not with atmospheric oxygen. The choice of laser irradiation wavelength is important for selective effect on O-VI and O-VII c...