Selective bias deposition of CuO thin film on unpolished Si wafer

Abstract

In order to enhance the performances of CuO-based surface-sensitive materials and devices, one feasible scheme is depositing CuO thin films on textured Si wafers to enlarge the specific surface area. In this work, the bias deposition of CuO thin film on unpolished Si wafer was carried out in a RF balanced magnetron sputtering system. The as-achieved CuO thin film was further characterized with scanning electron microscope, powder x-ray diffractometer and ultraviolet-visible spectrophotometer. It was found that the CuO thin film shows a pyramid-textured film morphology consisting of composite structures: a loose and porous thinner film at the bottom of bevel, a dense and compact thicker film at the top of bevel and on the underside, and many nanosheets standing on the film surface. The tip charging effect and bevel influence were discussed to reveal the selective deposition mechanism of CuO thin film on the unpolished Si wafer. It was also demonstrated that the unpolished rough Si wafer surface seems more suitable for the crystallization of CuO along (002) orientation rather than (111) orientation. Meanwhile, the CuO thin film on unpolished Si wafer exhibits the strongest absorption at the wavelength of ∼554 nm and a band gap of 1.94 eV, both of which show redshift relative to those of CuO thin film on polished Si wafer.