Enhanced Opto-electronic Properties of Nd Doped CuO Thin Film

Abstract

Here, pure, and Nd-doped CuO thin films with different composition (0.5 mol%, 1 mol%, 3 mol% and 5 mol%) were prepared following sol-gel spin coating route. X-ray diffraction analysis exhibited polycrystalline monoclinic structure of the films. Crystallite size and micro-strain were calculated from XRD analysis. As Nd doping was increased, crystallite size decreased for any addition beyond 0.5 mol%. Micro-Strain was also increased with increasing Nd doping indicating the lattice misfit because of size difference of Cu2+ and Nd3+. Optical properties of the pristine and Nd doped films were characterized using UV-visible spectrophotometry. The bandgap values were 1.92, 1.90, 1.87, 2.02 and 1.97eV for undoped, 0.5 mol%, 1mol%, 3 mol% and 5 mol% Nd doped films, respectively. Various optical parameters and dielectric constants were calculated for various optoelectronic applications. The topography of the films was studied using Atomic Force Microscopy and it revealed that the average roughness of the films varied in the range of 4.9 to 8.1nm. Electrical conductivity of the undoped film was increased from 0.315 to 0.596 Scm-1 for 5 mol% Nd doping which was measured using a 4-point probe method. Hall measurements showed an increment of carrier concentration by an order of 10 for the 5 mol % Nd doping compared to undoped CuO thin film, where charge carrier mobility was also increased from 0.102 to 0.453 cm2V-1s-1. However, for the maximum doping concentration of 5 mol%, the films remained p-type semiconductor confirmed by the positive value of the co-efficient RH.