Doubling the thermoelectric power factor of earth abundant tin nitride thin films through tuned (311) orientation by magnetron sputtering

Thermoelectricity has been considered a promising green energy source for mankind. This method of energy generation poses challenges due to scarcity of the constituent elements of the efficient thermoelectric materials. The development of high performance materials for thermoelectric generation is limited with the co-responsive nature of transport parameters. In this work, earth abundant tin nitride (Sn3N4) thin films were deposited by reactive radio frequency magnetron sputtering and investigated its thermoelectric response. The electron bands of the prepared thin films were actively aligned to optimize the trade-off between the Seebeck coefficient and electrical conductivity for the enhancement of power factor (S-2 sigma). The reduction in nitrogen gas pressure of reactive sputtering reduced both working pressure and the amount of reactive nitrogen. This experimental approach of combined effect introduced preferred orientation (PO) and stoichiometric variations simultaneously in the fabricated thin films. The increased scattering associated with preferred orientation and increased carrier concentration associated with stoichiometric variations converged the conduction band along with shifting of Fermi energy toward the conduction band minimum. The engineered band structure of tin nitride thin film realized over 2-fold hike in power factor up to 390 mu W/m-K-2 at 250 degrees C with a Seebeck coefficient of -144 mu V/K and resistivity of 53.11 mu Omega-m. This study reveals the potential nature of the earth abundant nitrides in the field of renewable energy generation. The experimental strategy adopted in this study provides an alternative approach to engineer the band structure of a thin film for optimized transport parameters. Published by AIP Publishing.