Investigation of the Influence of Au (Gold) Doping Concentration on the Structural, Morphological, Optical, and Electrical Parameters of an Al/Au:CuO/n-Si Heterojunction Device

In this investigation, we achieved successful deposition of nanostructured cupric oxide (CuO) thin films onto glass substrates through implementation of successive ionic layer adsorption and reaction (SILAR), all carried out at room temperature. This approach has proven to be highly efficient and yielded favorable results in terms of film quality and uniformity. A comprehensive investigation was conducted to analyze the effect of gold (Au) on the structural, morphological, optical, and electrical properties of nanocrystalline CuO thin films. The structural analysis confirmed that the films were polycrystalline, exhibiting a monoclinic crystal structure with preferential orientations along the (\(\overline{1}11\)) and (111) planes. The estimated crystallite sizes ranged from 20.37 to 30.77 nm, indicating the nanoscale nature of the films. Scanning electron microscopy/energy-dispersive x-ray analysis (SEM/EDX) was executed to reveal the Au dopant on the surface of CuO thin films. Surface analysis revealed the presence of uniformly dispersed CuO nanostructures across the film surfaces. Through optical investigations, it was observed that the bandgap energy of the CuO thin films decreased from 1.52 to 1.45 eV with increasing Au concentration. Furthermore, the average transmittance of the films exhibited a decrease from 4.9% to 1.3% as the Au concentration increased. The electrical properties of the Al/Au:CuO/n-Si heterojunction were studied using current–voltage (I–V) measurements for various light power densities. The Al/Au:CuO/n-Si heterojunction exhibited good photodiode behavior, with 3.44 A/W responsivity and 1.58 × 10¹⁰ Jones specific detectivity for the 2% Au-doped CuO interfacial layer.