Microstructures and optoelectronic properties of CuxO films deposited by high-power impulse magnetron sputtering

Abstract

Herein, a novel method of high-power impulse magnetron sputtering (HiPIMS) was used to prepare Cu2O thin films, which were deposited at ambient temperature without further thermal treatment. The films with varying optoelectronic properties as a function of oxygen flow ratio (fO2) were investigated. The results demonstrate that the film's performances are dependent on the film's composition and their crystallinity, which is influenced by the oxygen flow ratio. Cu2O-dominated films were fabricated in the oxygen flow range between 12.5% and 35%, whose values were used to determine their optoelectronic properties. Consequently, the films optoelectronic properties can be controlled by adjusting oxygen flow ratio. At low oxygen flow ratio (fO2 ≤ 10%), Cu-dominated films present n-type conductivity. With oxygen flow ratio increasing to above 15%, the films conductivity type changes from n-type to p-type due to the majority phase in the films changing from Cu to Cu2O. Meanwhile, the film's transmittance improves significantly from 0.28% for fO2 of 2.5% to the maximum value of 58.77% for fO2 of 30% resulting from the phase's transition upon increasing the oxygen flow ratio. When the oxygen flow ratio is at about 20%, a Cu2O film with optimal p-type conductivity of approximately 0.4 S × cm−1 is achieved at room temperature, which is the highest p-type conductivity reported in Cu2O film for the last few years.