Thin-film synthesis of metastable rocksalt MgSnN2 without epitaxial stabilization

Abstract

Metastable rocksalt-type MgSnN2 (rs-MTN) films were fabricated on amorphous substrates via the high-pressure heat treatment (HPHT) of wurtzite-type MgSnN2 precursor layers. HPHT caused a wurtzite-to-rocksalt transition, and more importantly, the rocksalt structure was retained upon depressurization, even without epitaxial constraints from the substrates. Single-phase rs-MTN films were obtained over a limited range of pressures and temperatures using HPHT. A pressure–temperature diagram for HPHT was also constructed, and the transition enthalpy barrier was estimated to be 0.21–0.23 eV. These results provide essential information on the kinetics of the wurtzite-to-rocksalt transition of MgSnN2.