Characterization of carrier-trapping phenomena in ultrathin chemical oxides using x-ray photoelectron spectroscopy time-dependent measurements

We report a technique to characterize carrier-trapping phenomena in ${\mathrm{SiO}}_{\mathrm{2}}$ by measuring the Si $\text{2p}$ core-level energy of Si substrates covered with thin ${\mathrm{SiO}}_{\mathrm{2}}$ layers as a function of x-ray irradiation time. It is found that the Si $\text{2p}$ peak energy, which corresponds to the band bending at the ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/Si}$ interface, changes as the x-ray irradiation time increases. We attribute this to carrier-trapping phenomena in ${\mathrm{SiO}}_{\mathrm{2}}.$ By using this technique, it is found that the carrier-trapping phenomena differ remarkably among several chemical oxides. We also discuss the atomic structure of the traps that cause the trapping phenomena.