Improved stability of metal-insulator-diamond semiconductor interface by employing CaF2/thin BaF2 composite insulator film

This letter presents a possible technical solution to obtain a mechanically and chemically tough BaF2/diamond interface for use in a metal/insulator/semiconductor (MIS) structure with excellent electrical properties. Presently, BaF2/diamond structures suffer from cracks and deterioration problems, although the interfaces are electrically stabilized to an acceptable quality. In the present work, we employed a composite film structure (CaF2/thin BaF2) as a gate insulator and its electrical properties were closely investigated by means of capacitance-voltage measurements. As long as BaF2 is thinner than 50 nm, the diamond MIS structure was electrically, chemically and mechanically stabilized. No particular difference was found in the surface state distributions between the BaF2/diamond and (CaF2/thin BaF2)/diamond interfaces.