ESCAで測定されたSi2p準位に与えるX線照射の影響

抄録

This study was carried out to find out the reasons for the discrepancies between the observed and expected carrier concentration dependences of kinetic energy of Si2p electrons from hydrofluoric acid treated Si as measured by ESCA. Experimentally, by changing the X-ray intensity and oxide thickness on Si, it was found that the above discrepancies are largely due to the effect of X-irradiation used for ESCA measurements. Theoretically, the electric potential distribution (band bending) near the Si surface due to X-irradiation was calculated by assuming a quasi-equilibrium state and using several simplifying assumptions. The changes in Si2p kinetic energies for various carrier concentrations caused by this band bending were then obtained in order to compare them with the experimental results. The calculated concentration dependence had all the features of the experimentally obtained results, and it was shown that the above discrepancies were due to two causes, namely, the increase in intrinsic carrier concentration near the surface (up to ∼10⁻⁶ m from the surface) due to X-irradiation and the electron emission from the region very near the surface (\lesssim10⁻⁸ m from the surface). These results show the importance of electric potential changes due to X-irradiation in the interpretation of obtained results, not only for insulators, but also for semiconductors. On the other hand, it is possible to obtain information on band bending and carrier concentration in the region very near the surface if measurements are carefully carried out.