Optical transmittance and electrical transport investigations of Fe-doped In2O3 thin films

We investigate the morphological, structural, optical and electrical transport properties of pulsed laser deposited pure and 10% Fe-doped indium oxide nanostructured thin films on the quartz substrates. The crystal structures and morphologies of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. XRD confirms that both the thin films are polycrystalline with cubic bixbyite geometry. The SEM and AFM analysis show nanostructures that are arranged in semi-regular pattern along with low surface roughness. The energy-dispersive X-ray spectrum verified the presence of In, Fe and O elements in the deposited films with their nominal percentage. X-ray photoelectron spectroscopy outcomes reveal a single valence state as observed in both In and Fe elements. A decrease in the optical band gap and a corresponding decrease in visible transmittance due to Fe doping have been inferred from optical transmittance measurements. It is observed that the doping causes a decrease in band gap, calculated by the Tauc plot. The Hall measurement exhibits that both the films are degenerate and indicate n-type semiconducting behavior with carrier density in the order of 1019 cm−3. Fe doping generates the higher resistivity along with a decrease in carrier concentration and mobility. Also, both of the films represent the normal semiconducting behavior with decrease in temperature, and their conduction mechanisms follow the Mott-variable range hopping (Mott-VRH) model at lower temperature.