Effect of Gd³⁺ doping on key structural, morphological, optical, and electrical properties of CdO thin films fabricated by spray pyrolysis using perfume atomizer

Gadolinium-doped cadmium oxide (CdO) thin films were fabricated by spray pyrolysis technique using a perfume atomizer on the glass and silicon substrates at 350 °C. The effect of increasing Gd concentration on the electrical, morphological, optical, and structural properties of deposited films was analyzed. Structural analysis of the pristine and doped CdO thin films showed cubic structures with preferred orientation of (200) direction. The estimated crystallite values ranged from 15 to 21 nm. The structural parameters like dislocation density, microstrain, a number of crystallites per unit area, and texture coefficient were also studied. Scanning electron microscope (SEM) images showed uniformly oriented and cauliflower-like nanostructures grown on the glass substrate for 3at.%-doped CdO films. The doped films' optical transmittance is found to be initially increased and systematically decreased with respect to doping concentrations. The band gap value is in the range of 2.42–2.30 eV for various Gd-doping concentrations (0, 1, 3, and 5%), respectively. The photoluminescence spectra (PL) of films were studied at room temperature and confirms the visible and green emission’ peaks are at wavelength 463 and 528 nm, respectively. From the Hall Effect studies, it proved that all the CdO films belong to an n-type degenerate semiconductor, and the low electrical resistivity value was around 3.64 × 10⁻⁴ Ω cm. The n-CdO/p-Si structure with different doping concentrations was subjected to photoconductivity studies and found that it is the maximum of 3% Gd concentration. Higher values of photo responsivity and quantum efficiency was found ~365 mA/W and ~76.64%, respectively, for 3at.% Gd-doped CdO films.