Copper oxide by spin-coating: Cost-effective deposition and post-annealing process for thin films with modulated Cu2O/CuO phase ratio

Copper oxide, in its cuprous (${\mathrm{Cu}}_{2}O$) and cupric (CuO) phases, is a promising material for energy and sensor applications due to its abundance, low cost, non-toxicity, and advantageous optoelectronic properties. However, its application in optoelectronic devices is limited by the lack of environmentally sustainable, cost-effective deposition methods capable of precise phase control. This work presents a spin-coating deposition method that utilizes non-toxic precursors in a cost-effective and scalable process. The method comprises two critical stages: (1) optimization of the spin-coating process by varying rotation speed (2000–6000 rpm) and cycle number (1–14 cycles) to produce homogeneous thin films with controlled thickness (20–175 nm) and low surface roughness (5 nm); and (2) post-annealing to achieve phase-specific control. Annealing at $300°C$ induces predominantly ${\mathrm{Cu}}_{2}O$, while biphased films are obtained at lower or higher temperatures. Optical and electrical characterization reveals a direct bandgap of 1.88 eV for ${\mathrm{Cu}}_{2}O$-dominant films and all films exhibit p-type conductivity, carrier mobility of 17–30 ${\mathrm{cm}}^2{V}^{-1}{s}^{-1}$, and carrier concentrations of $8\times 10^{13}$–$10^{15}{\mathrm{cm}}^{-3}$. This cost-effective and scalable method demonstrates precise phase control and material properties, highlighting copper oxide’s potential for next-generation optoelectronic devices.