Surface characteristics, optical and electrical properties on sol-gel synthesized sn-doped ZnO thin film

Un-doped ZnO and Sn-doped ZnO (SZO) thin films were synthesized using the sol-gel method. The surface morphology of the SZO films showed a large amount of crystallization. Doping with tin dopants not only reduced the surface roughness of the film, but also repaired defects in the pore structure. Notably, the SZO film with a crystallization temperature of 650°C possessed better crystallization and fewer defects when tin dopants were added. XPS analysis confirmed the presence of O-Sn⁴⁺ phases proving the contribution of tin doping on the electrical conductivity of the SZO films. With regards the PL spectra, luminescence in the Zn₂SnO₄ phase was observed and affected the red-shifted of broad visible emission. In addition, the 9 at% Sn doped ZnO (S₉ZO) film showed excellent optical transmittance, however the transmittance improved further when the trace of tin dopants (0.4 at%) and 2 at% In were doped in ZnO matrix (I₂S_0.4ZO).