Innovative Development and Characterization of Ni and Zn Co-Doped SnO₂ Thin Films via Dip-Coating for Cutting-Edge UV Photodetectors

In this recent study, thin films of pure tin oxide (SnO 2 ) denoted by TO and tin oxide doped with nickel (Ni) and zinc (Zn) at varying concentrations of 5 wt.%, 10 wt.%, and 15 wt.% were developed and characterized on ordinary glass substrates. The deposition of the films was conducted using the sol-gel technique (Dip-coating). These films are referred to as (Ni-Zn) co-doped tin oxide (NZTO) films that can be used in diverse applications such as gas and UV sensors. The effect of Ni/Zn co-doping on the structural, morphological, optical, and electrical properties of undoped SnO 2 was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. The electrical properties were further examined using the quadruple method. XRD analysis revealed that all samples were polycrystalline with a rutile-type tetragonal crystal structure, predominantly oriented along the (110) plane, but changed to (100) and (200) orientations with high doping contents. The grain size values exhibited a decreasing tendency with increasing co-doping content. The SEM images indicated that the films possessed a porous surface and were made up of well-defined and homogenously dispersed spherical and polyhedron-shaped nanoparticles, which were influenced by doping with Ni and Zn. The FTIR study showed that all the films exhibit the Sn-O-Sn, Sn-O, Sn-OH, and H-O vibration peaks. The NZTO films enhanced the crystal structure and raised the optical energy gap from 4.03 eV for TO to 4.09 eV for NZTO. The thickness also increased from d = 353.44 nm for pure TO films to d = 448.43 nm for films doped with 15% NZTO. The highest transmittance value was observed to be 93% for TO within the visible range. Hall effect measurements indicated that TO exhibited n-type conductivity and p-type conductivity when doped with 5%, 10%, or 15% NZTO. This allows photodetectors based on TO to show great sensitivity to UV light.