Rhodamine (B) photocatalysis under solar light on high crystalline ZnO films grown by home-made DC sputtering

ZnO thin films were deposited by home-made DC sputtering of zinc target under mixed gases (Argon, Oxygen) plasma on glass substrates. Films were deposited by varying oxygen partial pressure (PO2) from 0.09 to 1.3 mbar in the deposition chamber, at a fixed substrate temperature of 100 °C. The samples were characterized by photoluminescence (PL), X-ray diffraction (XRD), optical transmissions (UV–vis), scanning electron microscopy (SEM) and electrical (Hall effect) measurements. The results indicate that by varying the oxygen pressure in the deposition chamber, the films show a precise and well defined photoluminescence emissions for each range of pressure covering almost the entire visible domain (UV, UV-Violet, Violet, Blue, and Red) with high intensities. Moreover, the deposited films have different defects levels. The XRD analysis indicates that the films are well grown along the c-axis peak, but with different crystalline quality. Optical measurements reveal a high transmission, up to 90%, in the spectral region between 400 and 2500 nm and a large variation of the optical band gap (3.16–4.34 eV). As an application of the deposited ZnO films, the photo-catalytic degradation of a synthetic solution of Rhodamine B (RhB) poured on a ZnO thin film was successfully achieved and an elimination rate of 38% was obtained after exposing the film to solar light for 3 h.