Does scandium resemble transition or rare earth metals when it is grown on silicon surfaces?

Abstract

Scandium (Sc) has long been considered a rare earth (RE) element rather than a transition metal (TM) when grown on silicon (Si) surfaces, although little experimental evidence supports it. When scandium nitride (ScN) grown on Si is a promising buffer material for combining gallium nitride (GaN) and Si, a thin Sc silicide layer may be formed at the ScN/Si interface and, therefore, the electronic properties of Sc on Si are becoming an important issue to address. In this study, the interfacial atomic and electronic properties of Sc on n-type Si (111)-7 × 7 reconstructed surfaces have been studied by low energy electron diffraction and synchrotron radiation based high-resolution X-ray photoemission spectroscopy. By varying the Sc overlayer thickness, different silicide phases were observed and the Schottky barrier (SB) evolution was obtained. The SB evolution of Sc on Si is closer to TM than RE. This barrier may interfere with carrier transportation if GaN/ScN/Si tri-layered heterostructures are grown.