Preparation of Copper Oxide Film at Low Temperature in Basic Conditions on a Copper Substrate

Copper is widely used in both its metallic form and as oxide across numerous scientific and industrial domains. The primary copper oxides, cuprite (Cu₂O) and tenorite (CuO), naturally form on the copper surface and play a crucial role in advanced technologies, such as solar cells, lithium batteries, and sensors. Tenorite is appreciated for its optical properties, stability, low toxicity, and reactivity. While copper oxide thin films are traditionally synthesized through thermal treatments and oxidation in alkaline environments, these conventional high-temperature methods not only require significant energy consumption but can also compromise the metal-film interface. This study aims to develop a sustainable alternative approach for forming a homogeneous CuO layer on a copper substrate through environmentally friendly treatments based on low temperature, cost-effective, and time-saving procedures. Three different eco-conscious treatments were investigated: (i) immersion in NaOH basic solution, (ii) exposure to NaOH basic solution vapours, and (iii) a combined treatment involving both immersion and vapour exposure. This green synthesis approach significantly reduces energy consumption compared to traditional thermal methods while maintaining product quality. The surface oxide layer was investigated through an optical microscope (OM), scanning electron microscopy (SEM), spectrocolorimetric analysis, peel-off test, µ-Raman and X-ray photoelectron spectroscopy (XPS) analysis to investigate the surface oxidation state.