Effect of precursor molarities on structural correlation with optoelectronic property of Zn2SnO4 nanostructured thin films

Zinc stannate, Zn₂SnO₄ (ZTO) has been recognized as the potential transparent conducting oxide (TCO) having reliable optoelectronic properties to be used in device applications like photovoltaic and display devices. In this study, the role of precursor solution molarity on structure and optoelectronic characteristics of the synthesized ZTO films is reported. XRD results reveal polycrystalline structure of the samples featuring two dominant peaks corresponding to (311) and (222) planes of fcc inverse spinel structure. FESEM analysis shows variation in the microstructure of the films with solution molarity. The grain size has wide variations with a majority of large sized grains for highly precursor molarity. Raman spectroscopy observes the characteristic peaks of the cubic inverse spinel structure of ZTO and variation of their intensities with the precursor concentration. The samples with 0.1 M and 0.2 M are found to be highly transparent (∼80 %) with deterioration in transparency on either side. All the samples exhibit dual band gaps on account of the having the inverse spinel structure. The variation in solution molarity gave TCO films with electrical resistivity in the range of 10⁻³ Ω-cm and a carrier concentration of ∼10¹⁹ cm⁻³. The Zn₂SnO₄ sample with 0.2 M exhibited maximal mobility of 151 cm⁻³ along with minimal carrier concentration of 10¹⁸ cm⁻³. This work provides the optimized molarities and parameters that can be utilized in developing the future transparent conductors for the electronics application.