Structural, optical and electrical properties of copper (Cu) and [nickel (Ni), copper]: co-doped SnO2 nanoparticles prepared by sol–gel method.

In this work, the un-doped, Cu-doped, and (Ni, Cu) co-doped SnO₂ nanoparticles (NPs) were synthesized using the sol–gel method with a fixed concentration of copper dopant while varying the nickel concentrations. The structural, optical and electrical properties, as well as the surface morphology, were investigated systematically by various characterization techniques. The X-ray diffraction (XRD) study confirmed that the prepared samples had a tetragonal rutile crystal structure for all single-doped/co-doped and un-doped SnO₂ NPs. The XRD results further confirmed that the crystalline sizes varied from 16 to 10 nm with the concentrations of the dopants. The UV–Vis diffusion reflectance spectroscopy (DRS) analysis showed that the optical band gap was found to be decreased from 3.38 to 3.27 eV when the dopant concentrations were increased. The energy dispersive analysis of X-ray spectra (EDX) results confirmed the presence of the expected elements in the prepared samples. Three major photoluminescence (PL) emission peaks were observed in the visible region, with a small shift toward lower wavelengths with dopant and co-dopant concentrations. Chemical bonding and the position of the O–Sn–O bond at 600–660 cm⁻¹ were confirmed by the Fourier transform infrared spectroscopy (FTIR) study. The activation energies and conduction mechanisms of the prepared samples were investigated using the Hall Effect measurement method. The I–V studies confirmed that the prepared samples had a good ohmic contact behavior and the resistivity decreased significantly for co-doped sample. [ABSTRACT FROM AUTHOR]