The Effect of Transient Power Ramp-Up on Structural and Optical Properties of CuO Thin Films Prepared by Radio Frequency Magnetron Sputtering

Abstract

Transition metal oxides have found application as charge transport materials (CTMs) in perovskite solar cell devices due to their better environmental stability and superior electronic properties compared to organic CTMs. Many researchers have used radio frequency (RF) magnetron sputtering to deposit inorganic CTMs on inorganic layers. However, such efforts on perovskites have been limited by the distortion of high-energy ions of the sputtering gas energized by the RF power and temperature. The ions may also distort the interface between transparent conducting oxides and the charge transport layers, thereby increasing optical scattering. Thus, the effect of ramp power during RF magnetron sputtering deposition on the structural and optical properties of copper oxide thin films is investigated. While the optical transmittance of the films decreases with increased RF power, it remains the same for all ramped power films; however, it has a similar profile as the highest RF power film. As the ramp power increases, the X-ray diffraction shows that the films become more polycrystalline with a monoclinic crystal structure. The energy-dispersive X-ray spectroscopy results reveal that the atomic concentration of copper slightly increases with the RF power, whereas oxygen concentration slightly decreases.