Photoinduced optical second-harmonic generation of SiNO films deposited onSi < 111 > substrate

Optical photoinduced second-harmonic generation (PISHG) of SiON films depos ited on Si[111] substrates has been studied. Nitrogen laser (lambda=337 nm) was used as a source of pumping light. We have found that with an increase of photoinducing power and nitrogen-to-oxygen (N/O) ratio, the PISHG for p robe YAG-Nd laser (for the doubled frequency lambda=0.53 mu m) signal incre ases and achieves its maximum value at photoinducing power about 0.96 GW/cm 2. The maximal value of the PISHG was equal about 1 pm/V. With decreasing t emperature, the PISHG signal strongly increases below 28 K. Femtosecond pro be-pump measurements indicate the existence of the PISHG maximum at pump-pr obe time delay about 0.4 ps. We explain these dependencies within a framewo rk of the quantum chemical approach and molecular dynamics interface struct ure optimization. Role of photoinduced anharmonic electron-phonon interacti on is demonstrated. We have revealed that Si-N chemical bonds play a key ro le in the observed photoinduced nonlinear optics effect. (C) 2000 American Institute of Physics. [S0021-8979(00)02708-0].