A possible origin of core-level shift in SiO2/Si stacks

Abstract

Band alignments of SiO2/Si stacks with different SiO2 thicknesses are re-examined by X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy. The energy difference between core-levels of SiO2 and Si is found to decrease with thicker SiO2. A possible explanation based on surface gap states (SGS) and charge neutrality level (CNL) is proposed to elucidate band alignment of SiO2/Si. Due to lower CNL of SiO2 SGS than Fermi level of Si, electrons transfer from Si to SiO2 SGS. With thicker SiO2 fewer electrons transfer from Si to SiO2, resulting in larger potential drop across SiO2 and XPS results.