Electrical transport, microstructure and optical properties of Cr-doped In_2O_3 thin film prepared by sol-gel method

摘要

High transparent In_2O_3 and Cr-doped In_2O_3 (In_(2-x)Cr_xO_3) nanocrystalline thin films were prepared using a simple sol-gel method followed by a spin coating technique. The effect of Cr concentration on the structural, microstructure, electrical and optical properties of In_(2-x)Cr_xO_3 were systematically investigated using X-ray diffractometer (XRD), atomic force microscopy (AFM), UV-vis spectroscopy, field emission scanning electron microscopy (FESEM) and Hall effect technique. The films have good crystallization with preferred orientation to (222) direction. The lattice parameters, o, of In_2O_3 system increased at lowest dopants (x ? 0.025) and decreased as the dopant was further increased. The optical transmittance of films increased up to 98% for x = 0.05 and decreased for further Cr concentrations. From AFM measurement the films nanocrystals morphology was depending on Cr concentrations. The band gap was around 3.76 eV for pure and with x ≤ 0.075 however it increased. The effect of Cr concentrations on conducting mechanisms of In_2O_3 film has been investigated from 80 to 300 K using thermal activated conduction band and hopping models. The films, at x = 0.0-0.075, have typical semiconductor behaviour. Three different conducting mechanisms have been estimated. All thermal activation energies and conduction hopping parameters have been determined and analysed in details.