Time-dependent second-harmonic generation from the Si–SiO_2 interface induced by charge transfer

Abstract

We have observed that the second-harmonic signal generated from oxidized Si(001) varies on a time scale of several seconds in experiments involving a fundamental beam of lambda = 770 nm, 110-fs pulses at 76 MHz. We suggest that the temporal behavior arises from absorption of weak (<100-fW average power) third-harmonic light generated in air or in the sample, inducing charge transfer across the Si-SiO(2) interface and trapping in the oxide layer. Detrapping has been determined to take several minutes.