Epitaxial growth of high-quality Mg₃Sb₂ thin films on annealed c-plane Al₂O₃ substrates and their thermoelectric properties

High-quality epitaxial Mg 3 Sb 2 thin films are promising thermoelectric materials to enable practical applications of compact and environmentally friendly thermoelectric conversion at RT. In this study, high-quality single-crystal Mg 3 Sb 2 with high c-plane orientation was epitaxially grown directly on annealed c-Al 2 O 3 substrates without passive layers. These thin films exhibited about three times higher thermoelectric power factor than any previously reported values due to high carrier mobility. The ultra-smooth surface of the annealed c-Al 2 O 3 substrate facilitated the formation of high-quality Mg 3 Sb 2 thin films without passive layers or polycrystalline interfaces that could be carrier scatters.