Structural and Optical Characterization of Gd Doped NiO Thin Films Deposited by Spin Coating Technique

Abstract

The NiO films exhibit excellent optical and electrical properties due to their wide bandgap and p‑type semiconducting behaviour, making them suitable for optoelectronic and TCOs. Furthermore, the intrinsic properties of NiO are enhanced by doping with suitable elements. Pristine and Gd-doped NiO (Ni_1–xGd_xO; x = 0, 0.02, 0.04, and 0.06) films. The various doping concentrations are deposited using the spin deposition technique. The detailed effects of Gadolinium (Gd) doping in a NiO matrix are investigated using structural, optical, and photoluminescence analysis. The XRD results show the average crystallite size varying from 14 to 8.7 nm for pure and Gd-doped NiO films with a face-centred cubic polycrystalline nature. The Raman spectroscopy analysis confirms the quality (purity) of the prepared thin films, showing Ni–O first-order modes that shift to higher wave numbers with Gd doping. FTIR analysis exhibits Ni–O-related vibrational bands in the range of 555 to 735 cm^–1 and other vibrational bands linked to various functional groups. The UV-visible spectra reveal the highest average transmittance of around 90% for films with Gd doping up to 4%. The energy gap evaluated utilizing Tauc’s plot analysis, varies from 3.52 to 3.56 eV for pure and doped films. From the PL spectra, near band edge emission peaks (363 nm) and other structural defects-related emission peaks are observed. The results suggest that by varying the dopant concentration, the structural and optical parameters can be modified. These films have the potential to be used in optoelectronic and catalytic devices.