Fyzikální ústav Akademie věd ČR

Seminar Wednesday, 23/06/2010 13:00 - 14:30

Speakers: Dr. Victor Sokolov (Institute of Metal Physics UD RAS, Yekaterinburg, Russia)
Place: Seminární místnost 117 ve Fyzikálním ústavu Na Slovance
Organisers:
   Division of optics
Presented in English

Dilute magnetic semiconductor Zn_1-xMn_xO is one of the most intensively studied materials for opto- and spin electronic applications where ferromagnetism retained to practical temperatures (Т_с > 300К) has been predicted theoretically. Surprisingly, its properties are turned out to be appreciable differ from those in Zn_1-xMn_xS and Zn_1-xMn_xSe and it is believed that ZnO:TrM belongs to the new little studied family of magnetic semiconductors with strong d-p hybridization [1]. Characteristic feature of such compounds is the appearance of the localized Zhang-Rice-like (Z-R) states in the forbidden gap arising due to strong exchange coupling of 3d localized spin of impurity centers and valence band holes [1]. Presence of Z-R states leads to pronounced shift of excitonic lines to the high energies with Mn concentration as it was recently shown for Zn_0.99Mn_0.01O nano-powders [2] and Zn_1-xMn_xO films for x< 0.05 [3]. Satisfactory evidences of the strong d-p hybridization Zn1-xMnxO reveal emission and excitation luminescence spectra of Zn_0.99Mn_0.01O nanocrystals [3,4] too. It was found that excitation spectrum of Zn_1-xMn_xO cardinally differs from that for intra-center emission of Mn²⁺ (⁴Т₂ → ⁶А₁) in Zn_1-xMn_xS. This allowed us to conclude that appearance of the emission peak at 2.9eV and excitation peaks at 3.9eV, 4.5eV and 5.3eV in photoluminescence of Zn_1-xMn_xO is the sequence of strong d-p hybridization and characteristic energy structure of MnO₄ clusters.

1. T. Dietl, Phys.Rev. B, 77, 085208 (2008).
2. V. I. Sokolov, A. Ye. Yermakov, M. A. Uimin, A. A. Mysik, V. A. Pustovarov, M. V. Chukichev and N. B. Gruzdev, J. of Lumin. 129, 1771 (2009).
3. V. I. Sokolov, A. V. Druzhinin, N. B. Gruzdev, A. Dejneka, O. Churpita, Z. Hubicka, L. Jastrabik, and V. Trepakov, Phys. Rev. B 81, 153104 (2010)
4. V. I. Sokolov, A. Ye. Yermakov, M. A. Uimin, A. A. Mysik, V. A. Pustovarov, N. B. Gruzdev and V.T. Surikov, Phys. Status Solidi C, 7, 1589 (2010)