Growth of Cu2InO4 thin films on Si substrate by thermal evaporation technique and enhancement of thermoelectric properties by post-growth annealing

Abstract

Thin films of Cu2InO4 were grown by thermal evaporation on Si substrate using tube furnace. Cu and In metals were evaporated in the tube furnace having pressure 0.2 × 10−2 Torr and the oxygen gas flow rate was set 60 standard cubic centimeters (sccm). The post-growth annealing in oxygen environment was performed at different temperatures ranging from 600 to 800 °C for 1 h in programmable furnace. The X-Ray Diffraction (XRD) data confirmed that as grown sample showed the amorphous nature, but it was converted into crystalline at higher annealing temperatures (700–800 °C). Raman spectroscopy measurements further confirmed the XRD results which showed a peak at 305 cm−1 at higher annealing temperatures, which is related to the Cu2InO4 structure along with Si peak at 521 cm−1. Photoluminescence spectroscopy (PL) data was demonstrated a band to band emission of Cu2InO4 at 1.9 eV and the intensity of this band was enhanced with the annealing temperature. XRD, Raman spectroscopy and PL results suggested that the structure of grown thin films was improved with increasing annealing temperature. After structure verification, In metal contacts were fabricated on all samples to investigate the temperature dependent thermoelectric properties. The Seebeck coefficient of Cu2InO4 thin films was found to be increased with annealing as well as measurement temperature. The reported results were explained according to charge mobility engineering, which was reported earlier by our group. We have also performed Hall measurements to strengthen our argument.