Effects of oxygen ion implantation in spray-pyrolyzed ZnO thin films

ZnO thin films, prepared using the chemical spray pyrolysis technique, were implanted using 100 keV O+ ions. Both pristine and ion-implanted samples were characterized using X-ray diffraction, optical absorption, electrical resistivity measurements, thermally stimulated current measurements and photoluminescence. Samples retained their crystallinity even after irradiation at a fluence of similar to 10(15) ions/cm(2). However, at a still higher fluence of 2 x 10(16) ions/cm', the films became totally amorphous. The optical absorption edge remained unaffected by implantation and optical absorption spectra indicated two levels at 460 and 5 10 nm. These were attributed to defect levels corresponding to zinc vacancies (V-Zn) and oxygen antisites (O-Zn), respectively. Pristine samples had a broad photoluminescence emission centred at 517 rim, which was depleted on implantation. In the case of implanted samples, two additional emissions appeared at 425 and 590 nm. These levels were identified as due to zinc vacancies (V-Zn) and oxygen vacancies (V-Zn), respectively. The electrical resistivity of implanted samples was much higher than that of pristine, while photosensitivity decreased to a very low value on implantation. This can be utilized in semiconductor device technology for interdevice isolation. Hall measurements showed a marked decrease in mobility due to ion implantation, while carrier concentration slightly increased. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.