Influence of copper doping on structural, morphological and optical properties of tin oxide (Sn_1−xCu_xO_2−δ)

The primary goal of this paper is to study a few advantages of bulk nanoparticles of Cu-doped SnO₂ using the solid-state reaction method. Many innovative methods were employed to evaluate the special tuning of the bandgap and other structural and morphological properties of the material. X-ray diffractometer (XRD) confirmed that tin oxide has a rutile-type tetragonal-shaped structure with space group P4₂ \(/\) $/$ _mnm. The average crystallite size was calculated which was found to increase from 53 to 80 nm by increasing the Cu-doping from x \(=\) $=$ 0 to x \(=\) $=$ 0.30. SEM images specified that nanoparticles are inhomogeneous and densely close to each other and the average particle size was found to be in the range of ~225–430 nm. Transmission electron microscopy (TEM) images showed the grains present in a few cubic and spherical shapes and grain size was increased (~20–90 nm) with doping of copper in the SnO₂ lattice. UV–Vis spectroscopy showed that the band gap increased from 3.531 to 3.701 eV for pure SnO₂ and Cu-doped SnO₂, respectively. XPS identified the electronic state of Sn as well as Cu atoms as \(4^{+}\) $4^{+}$ and \(2^{+}\) $2^{+}$ , respectively. Raman spectroscopy showed that only three vibrational modes, i.e., A_1g, B_2g and doubly degenerate E_g, exist in a sample.