UV and IR emission intensity in ZnO films, nanorods, and bulk single crystals doped with Er and additionally introduced impurities

Abstract

For ZnO films, nanorods, and bulk single crystals doped with Er⁺ ions, it is shown that the effect of codopants introduced into the cation and ion sublattices and the observation of a high-intensity emission band at the wavelength λ_max = 1535 nm are defined by the local environment of the Er⁺ ion. Doping of the films and single crystals with Er⁺ ions by diffusion brings about an infrared (IR) emission band with a low intensity because of an inadequate concentration of impurity ions. The emission intensity of this band can be raised by introducing additional Ag, Au, or N⁺ impurities into the ZnO films. The UV-emission intensity of the Er-doped films and single crystals at λ_max = 368–372 nm is identical to that of the undoped films. ZnO nanorods doped with Er only or together with Al or Ga codopants exhibit only one IR band (at λ_max = 1535 nm), whose intensity decreases upon the introduction of codopants. Doping of the nanorods with the N⁺ gaseous impurity during growth (930 < T < 960°C) and then with the Er⁺ impurity by diffusion does not yield a substantial increase in the IR-emission intensity compared to the that of the corresponding band for nanorods not doped with the N⁺ impurity. In the Er-doped nanorods, whose photoluminescence spectra exhibit a high-intensity band at λ_max = 1535 nm, the UV emission band at λ_max = 372 nm is practically lacking.