A systematic influence of Cu doping on structural and opto-electrical properties of fabricated Yb2O3 thin films for Al/Cu-Yb2O3/p-Si Schottky diode applications

In the present work, transition metal doped rare earth metal oxide (Cu-Yb2O3) thin films have been effectively synthesized on a large scale using low-cost jet nebulizer spray pyrolysis (JNSP) route at different copper (Cu) doping concentrations (0, 1.5, 2.5, 3.5, and 4.5 wt%) with optimized substrate temperature of 550 °C. The structural, morphological and opto-electrical properties were investigated using various characterization techniques. The X-ray diffraction (XRD) profile indicates the polycrystalline nature of all the deposited films with a cubic phase and the size of crystallites is found to increase from 11 to 31 nm. The field emission scanning electron microscope (FESEM) images reveal that the Cu doping has significant impact on the surface morphology of Cu-Yb2O3 films. The atomic force microscope (AFM) analysis exposed higher roughness value for 4.5 wt% of Cu-Yb2O3 films. The elemental composition study approves the presence of Yb, Cu and O in the film. The transmittance and indirect optical energy gap of Cu-Yb2O3 films have been analyzed by UV–Visible spectroscopy which established the systematic band gap reduction of Yb2O3 thin films from 3.68 to 3.14 eV with increasing Cu concentrations. The DC electrical studies showed a maximum conductivity and minimum average activation energy for 4.5 wt% of Cu-Yb2O3 film. The electrical characteristics of the fabricated Al/Cu-Yb2O3/p-Si Schottky diode was investigated using current–voltage (I-V) measurements performed under dark and light conditions. The ΦB (0.911 eV in dark & 0.754 eV in illumination) and minimum n values (2.120 in dark and 1.757 in illuminations) were obtained for MIS diode having Cu doping concentration of 4.5 wt% in Yb2O3.