PHOTO-STIMULATED STRUCTURAL-CHANGE IN A-SIO2 FILM WITH UNDULATOR RADIATION

We have studied the change in the principal peak of the infrared spect rum, the refractive index, and the thickness in amorphous SiO2 (a-SiO2 ) caused by the irradiation of high-energy photons from undulator radi ation. a-SiO2 films are fabricated by the thermal oxidation of silicon wafers at 1000 degrees C in an oxygen atmosphere. Illumination in the vacuum ultraviolet region is per formed with an Onuki-type undulator installed in the elelctron storage ring (NIJI II) in the Electrotechni cal Laboratory (ETL). A downshift to the lower energy of the principal peak at 1080cm(-1) in the IR spectrum by illumination implies a reduc tion of the mean Si-O-Si bond angle. We assume that the network struct ure in the illuminated a-SiO2 was very close to that in densified a-Si O2.