Exploring the p-Type to n-Type Transition in CuO Thin Films Via Zn Doping: Insights from M-SILAR Synthesis

A modified successive ionic layer adsorption and reaction (M-SILAR) method has been used for the fabrication of undoped and Zn-doped copper oxide CuO thin films with different concentrations of zinc (0%, 2%, 4%, 6%, 8%, and 12%). X-ray diffraction and Raman spectroscopy analyses revealed the polycrystalline nature of the thin films and confirmed that Zn ions were incorporated into CuO without altering its monoclinic phase, along with a reduction in crystallite size as the Zn concentration increased. Notably, no Cu2O or other impurities were detected. Scanning electron microscopy and atomic force microscopy revealed changes in morphology, including nanorod shapes, and indicated decreased surface roughness and grain size, with the smallest grains observed at 8% Zn doping. The optical bandgap increased from 1.55 eV to 1.62 eV at 8% Zn doping. Hall effect measurements indicated that doping concentrations below 8% retained their p-type conductivity, with 6% Zn identified as the optimal doping level, achieving the highest carrier concentration and mobility. However, at 12%, a transition to n-type occurred. This shift suggests that higher Zn content could expand the applicability of CuO beyond photovoltaics, offering new possibilities for device engineering. The findings provide a fresh perspective on tailoring CuO thin film electrical behavior through controlled Zn incorporation.