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Tunable nonlinear optical absorption in semiconductor nanocrystals doped with transition metal ions J. Appl. Phys. 112, 074305 (2012) Temperature dependent photon echoes of a GaN thin film Appl. Phys. Lett. 101, 142102 (2012) Energy transfer in finite-size exciton-phonon systems: Confinement-enhanced quantum decoherence J. Chem. Phys. 137, 114702 (2012) Importance of excitonic effects and the question of internal electric fields in stacking faults and crystal phase quantum discs: The model-case of GaN Vibrational states interacting with a donor exciton in the compound ZnO:Co are revealed by the sensitive method of field exciton-vibrational spectroscopy. The vibrational modes of the electroabsorption spectrum of the compound ZnO:Co in the region of the donor exciton are given an interpretation based on the existing data on the symmetrized local density of states of the compounds ZnO and ZnO : Ni 3+ . The results are compared with the known data for II-VI:Ni compounds in the case of an acceptor exciton. The position of the donor level of the Co 2+ ion relative to the bottom of the conduction band in the given compound is determined and found to conform well to the universal trend for donor levels of 3d ions in II-VI compounds.

In this paper the results of the study of optical absorption, photo-EPR signals and magnetic measurements of hydrothermal single crystals of zinc oxide doped with manganese were presented. Several lines were detected in optical absorption spectra at the temperature of 4.2 K and 77.3 K for σ- and π- polarizations of light in a 1.72–2.3 eV spectral range. These lines are attributed to a donor exciton [(d5 + h)e] that emerges as a result of the Coulomb binding of a free s electron and a hole, which is localized on p–d hybridized states. Properties of these lines are significantly different from the properties of lines of donor and acceptor excitons in II-VI:3d compounds. In EPR-spectra of Zn1-x Mn x O crystals the intensity of allowed and forbidden EPR-signals of Mn2+ (d 5)-ions does not change under the illumination while the intensity of EPR-signals of unintentional Fe3+ (d 5)-ions decreases by 70 %. The value of the magnetic susceptibility of Zn1-x Mn x O (x = 0.0009) is in linear dependence with temperature, which agrees with the Curie equation. Temperature dependence of the inverse value of the Mn2+ magnetic susceptibility indicates that the exchange interaction in ZnO:Mn crystals is absent. New experimental results allow us to assume that investigated Zn1-x Mn x O (x = 0.0009) samples are semiconductors in the forbidden gap of which the donor level of d5/d4 does not exist. The hybridization of d5 states of Mn2+ and p states of the nearest four oxygen ions O2- leads to pushing out the antibonding DBH-states (d 5 + p) into the forbidden gap. The transitions of electrons from DBH-states to the conduction band provide a broad band of the impurity absorption in ZnO:Mn. Below this band we observed a, b, c and d lines, which are called dbh-donor excitons [(d5+h)e].