Observation of interface dipole modulation in an Al2O3/SnOx/SiO2 stack

Interface dipole modulation (IDM) has predominantly used TiO2 as the IDM layer, and changes in the valence state of TiO2 critically affect device operation. This study demonstrates the use of SnOx instead of TiOx for IDM and elucidates the underlying mechanism in detail. Metal–oxide–semiconductor capacitors with an Al2O3/atomic-layer-thick SnOx/SiO2 stacked structure were fabricated and analyzed. Capacitance–voltage measurements revealed that the polarity of the interface dipole layer changed depending on the gate bias. Hard x-ray photoelectron spectroscopy measurements demonstrated the switching of the potential profile within the Al2O3/SnOx/SiO2 stack. These results indicate that SnOx can be used as an IDM layer and suggest that not only TiOx and SnOx but also other oxide materials capable of adopting various oxidation states are potential candidates for IDM.