Electronic Structure and Thermoelectric Properties of Mg2Sn Films Fabricated by Using Co-Sputtering Process With Stoichiometric Modification

Colossal values of the Seebeck coefficient were first discovered in Mg-poor Mg
₂
Sn films in the temperature range 600–700 K. Cubic and orthorhombic structures of the Mg
₂
Sn films for solid-state thermoelectric energy conversion devices were prepared by radio frequency (RF) magnetron co-sputtering. The Mg-Sn films showed a structural phase transition between the metastable orthorhombic and the stable cubic structures as the atomic ratio Mg/Sn varied near the stoichiometric ratio. The Mg-poor orthorhombic Mg-Sn films transited from p-type to n-type conductivity at 500 K and exhibited colossal values of the Seebeck coefficient and power factor in the temperature range 600–700 K. The colossal Seebeck coefficient, which exceeded −10 mVK
⁻¹
, indicates long-term stability over a wide temperature range. Furthermore, the energy band structure and density-of-state were calculated for the cubic and the orthorhombic Mg
₂
Sn using the first-principles calculation with the Perdew-Burke-Ernzerhof (PBE0) hybrid functionals, which yielded results that were consistent with the experimental data.