Influence of thickness on crystallographic, stereometric, optoelectronic, and electrochemical characteristics of electron-beam deposited indium tin oxide thin films

Abstract

High transparency, low resistivity, and smooth surface of transparent conductive oxides like ITO (Indium Tin Oxide) thin films yet are desired for achieving diverse fields of optoelectronic and energy storage usages. Here, it was illustrated how the thickness variations of ITO films during deposition onto a substrate of glass through the electron beam evaporation method could influence the main features of the films. For acquiring this goal, besides optoelectronic, crystallographic and stereometric analyses of surface morphology, electrochemical investigations of the films were performed. X-ray diffraction or XRD results of ITO films revealed along with growth processing, crystallite size value, inter-planar spacing, and lattice constant increased. However, strain, dislocation density, and texture coefficient of the films showed a different trend. The maximum crystalline size (41 nm) and minimum micro-strain (3.1939 × 10−3) were observed in the thickest ITO film (140 nm). Spectroscopic data confirmed the lowering transparency of ITO films during the growth of thicknesses (from 95.56 %to 82.50 %). The conductivity examinations of the films revealed with increasing the thickness, sheet resistance decreased. The highest resistivity was related to 50 nm ITO film, 79 Ω/□, while the resistance of the ITO film with 140 nm thickness was 32 Ω/□. Functional surface and volume parameters results as well as monofractal dimension outcomes, derived from atomic force microscopy (AFM) data, described the thicker ITO films had smoother surface and lower porosity. Furthermore, the electrochemical analyses include electrochemical impedance spectroscopy and cyclic voltammetry studies verified the increasing the conductivity of the films during thickness growth.