Self-activated growth of cubic AlScN films from molecular nitrogen without plasma

Abstract

Self-activated growth of ScN was recently reported owing to the ability of scandium to self-catalyze N2 bond breaking, facilitating nitride film growth from molecular N2 without plasma. In this report, we expand this novel synthesis method to explore the possibility of self-activated growth of aluminum–scandium–nitride, an emerging ternary nitride system with enhanced functionalities. We find that the rock salt AlScN film growth of low Al composition from 0% to 48% is possible by self-activated growth. The cubic rock salt AlScN films are phase pure up to 21% Al, whereas mixed rock salt AlScN and intermetallic cubic AlxSc phases appear in films with 28% to 48% Al. Self-activated nitride crystal growth was not observed for films grown with high Al content of 93.7% and 100% Al, which showed cubic AlxSc and FCC α-Al phases, respectively, without any sign of nitrogen incorporation. Lattice parameters of crystalline rock salt AlScN films decrease with increasing Al composition. The self-activated AlScN films, as well as cubic AlxSc and FCC α-Al phase, exhibit twinning and are epitaxial to the 6H-SiC substrate. The findings open up new avenues for the ultralow-energy synthesis of ternary nitrides and beyond.