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

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 $\lambda_{\operatorname{max}}$ = 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 $\lambda_{\operatorname{max}}$ = 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 $\lambda_{\operatorname{max}}$ = 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 $\lambda_{\operatorname{max}}$ = 1535 nm, the UV emission band at $\lambda_{\operatorname{max}}$ = 372 nm is practically lacking.