Effect of La doping on the structural, optical and electrical properties of spray pyrolytically deposited CdO thin films

Solution based chemical spray pyrolysis technique was employed to deposit lanthanum (La) doped cadmium oxide (CdO) thin films on soda-lime microscope glass slides. X-ray diffraction (XRD) analysis revealed that deposited films are polycrystalline having cubic crystal system. The undoped and 0.25 wt % La doped CdO films show relatively intense (111) plane, which is shifted to (200) plane for doping concentrations greater than 0.50 wt %. The parameters such as lattice constants, crystallite size, micro-strain, dislocation density and texture coefficient are extracted from XRD data. Field emission scanning electron microscopy analysis confirmed the smooth and uniform surface. Energy dispersive spectroscopy analysis was used to estimate the preliminary information on elemental composition. The deposited undoped and La doped films possess optical transmittance ranging 78–82% in the visible and near infrared (NIR) region. The estimated direct optical band gap of undoped and La doped CdO thin films is varied between 2.38 eV and 2.46 eV. Hall measurements confirmed the n-type conductivity in the films. The doping-modulated mobility and carrier concentration are ranging 68 cm²/V s–78 cm²/V s, and 1.0 × 10²⁰ cm⁻³–4.06 × 10²⁰ cm⁻³, respectively. Room temperature micro-Raman studies confirmed the metal oxide (Cd[sbnd]O) bond vibrations in deposited films. A high figure of merit (11.45 × 10⁻³ Ω⁻¹) is obtained from 1.0 wt % La doped CdO film.