Emission, Er ion defects and structure of ZnO nanocrystal films prepared by ultrasonic spray pyrolysis

Abstract This work focuses on the investigation of near band edge (NBE) and Er ion related emissions, morphology and structure of Er-doped ZnO nanocrystal (NC) films prepared by ultrasonic spray pyrolysis with the different Er contents. The scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) methods have been used. It is revealed that the crystal structure of ZnO:Er films can be improved at low Er-doping (≤ 2 at%), when Er ions occupy the Zn vacancies with the formation of the substitutional Er Zn defects. Simultaneously, the PL intensity of NBE emission enlarges and the PL intensity of green PL band, connected with native deep defects, decreases. Meanwhile, the IR emission via the 4f intra-shell optical transitions ( 4 I 13/2 – 4 I 15/2 ) in Er ions at this doping is insignificant. The PL intensities of NBE emission, all visible and IR emission bands, connected with the 4f inner-shell optical transitions in Er ions, have enlarged essentially at higher Er-doping (