Characterization of SiO2/Si interfaces by using X-ray photoelectron spectroscopy time-dependent measurement

We report the results of the X-ray photoelectron spectroscopy (XPS) time-dependent measurement of expanded X-ray irradiation times ranging from 1 to 10, 000 min. It was found that the Si 2p peak binding energy of a Si substrate covered with an ultrathin SiO2 film first increases, then decreases, and again increases during X-ray irradiation. A shift toward a higher binding energy indicates that the amount of positive charge in the SiO2 film is increasing, and a shift toward a lower binding energy indicates the amount of negative charge in the SiO2 film is increasing. The complex hole/electron trap phenomena in ultrathin SiO2 film can be explained by a trap generation model of the SiO2 film during X-ray irradiation.