Improved transparency and conductivity in copper chromium oxide coatings through aliovalent doping and stoichiometry control

Abstract

Copper delafossites are well known p-type oxide semiconductors with transparent conducting properties, displaying high electrical conductivity, optical transparency, and wide band gap (∼3 eV), and as such they have potential applications in various optoelectronic devices. However, their performance is still inferior compared to their n-type counterparts. In this study, we investigate the deposition of delafossite copper chromium oxide (CuCrO₂) thin films employing a sol–gel precursor solution in conjunction with ultrasonic spray pyrolysis. Our research focuses on assessing the influence of magnesium doping on the structural, electrical, and optical properties of the CuCrO₂ coatings. We employ a range of characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrical conductivity, and optical spectroscopy. Continuous, dense and polycrystalline thin films of phase pure delafossite films are obtained across all conditions, regardless of the addition of Mg dopants. A copper-poor precursor formulation was chosen to enhance the visible transparency of the coatings. Importantly, the electrical properties of CuCrO₂ thin films exhibit substantial enhancement following the introduction of Mg. Our optimized films exhibit conductivity of 52.8 S cm⁻¹, visible transmittance greater than 50%, and an optical band gap of approximately 3 eV. These noteworthy findings constitute as a promising foundation for the development of high-performance p-type transparent conductors.