TRANSMISSION AND REFLECTION SPECTRA OF ZINC OXIDE IMPLANTED WITH A HIGH DOSE OF COBALT IONS

Abstract

Optical transmission and reflection spectra of monocrystalline plates of zinc oxide (ZnO) implanted with 40 keV Co⁺ ions to high doses of (0.5-1.5)×10¹⁷ cm^-2 are presented. A decrease in the transmission value and the shift of the optical transmission edge to the long-wavelength region with increasing of the dose are observed in transmission spectra. Three absorption bands in the range of 550-680 nm are also observed in transmission spectra. The bands and their positions are typical for optically active Co²⁺ ions in the zinc cation substitution positions in the ZnO matrix. The reflection coefficient of the implanted side of the ZnO plate increases monotonously with the dose values. In both, the initial and implanted ZnO plates, a characteristic structure at λ = 375 nm due to exciton reflection is observed when recording the reflection spectra from the reverse (non-irradiated) side. Modeling of light transmission and reflection in cobalt-implanted ZnO samples was carried out within the framework of a three-layer model, in which the first surface layer contains cobalt nanoclusions, the second, deeper layer is a solid solution of cobalt ion substitution in the ZnO matrix, the third layer is the unradiated part of the ZnO plate. As a result of modeling, effective refractive indexes of two ZnO layers containing implanted cobalt admixture in different phase states were determined.