Investigation of Structural, Morphological, and Photoluminescence Properties of Nanocrystalline Copper doped Tin Oxide Thin Films Grown by RF Sputtering Method

This research investigates the structural, morphological, and optical properties of SnO₂ and Cu-doped SnO₂ films deposited on glass and FTO substrates using the RF sputtering technique. The Cu-doped samples were subsequently annealed in an oxygen flow at temperatures of 400 and 500 °C. X-ray diffraction (XRD) analysis revealed that pure SnO₂ thin films exhibited an amorphous structure on both substrates. In contrast, the Cu-doped SnO₂ sample on the glass substrate maintained its amorphous state, while the sample on the FTO substrate transitioned to a tetragonal rutile structure. Thermal annealing further induced a transformation to a tetragonal rutile structure for samples on both substrates. Energy dispersive spectroscopy (EDS) confirmed the incorporation of Cu into the SnO₂ films. The estimated crystallite sizes ranged from 16 to 20 nm for the glass substrate and from 20 to 31 nm for the FTO substrate. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses demonstrated uniform surface morphology with a smooth texture and strong adhesion to the substrates. The band gap energy (Eg) values for the unannealed samples were found to be 3.52, 3.40, 3.50, and 3.29 eV. Notably, Cu doping and the deposition of SnO₂ films on FTO substrates resulted in a reduction of the band gap. These findings provide valuable insights into the effects of Cu doping, annealing, and substrate type on the structural and optical properties of SnO₂, paving the way for advanced optoelectronic applications.