Direct growth of ZnSnO nano-wires by thermal evaporation technique for thermoelectric applications

Abstract

In this research, we have successfully grown the ZnSnO nano-wires by simple thermal evaporation technique and reported the highest Seebeck coefficient and power factor for first time. The ZTO nano-structures were grown by a simple thermal evaporation method using direct evaporation of Zinc and Tin metal powders under constant oxygen flow rate of 100 sccm in a tube furnace. The post growth annealing was performed in the temperature ranges of 600–900 °C with a step of 100 °C in the programmable muffle furnace. The structural, electrical, morphological and thermoelectric properties of as grown and annealed samples were analyzed by X-Ray Diffraction, Raman spectroscopy, Scanning Electron Microscopy, Hall data and Seebeck effect. The XRD results confirmed the formation of Wurtzite hexagonal structure and the vibrational mode of ZTO at 437 cm−1 is verified by Raman spectroscopy measurements. It was also observed that the crystal structure of ZTO was improved with annealing temperature. SEM micrographs showed the nanowires like morphology of the un-annealed sample but it transformed into nano-crystalline grains by post growth annealing. Seebeck data demonstrated that the values of Seebeck coefficient, electrical conductivity and power factors were found to be increased with annealing temperature because Sn atoms get more thermal energy at high temperature and contribute in the carrier concentration.