SiO2/Si interface properties using positrons

Positron-annihilation spectra are used to identify interface states in a 110-nm-thick, thermally grown (dry, no HCl) ${\mathrm{SiO}}_2$/Si(100) system. A normalized shape parameter (S parameter) is used to characterize the positron-annihilation spectra. The interface-state-density variation under a low-temperature annealing (20 °C–500 °C) is shown to be correlated with the variation in the intensity of the interface shape parameter. Activation and passivation of interface states by atomic hydrogen are demonstrated by repeated in situ hydrogen exposure and vacuum anneal. The present study shows that characterizing the interface states with positron-annihilation techniques opens an avenue for studies involving interface states without the need for a gate electrode.