Nature of red luminescence band in research-grade ZnO single crystals: A “self-activated” configurational transition

Abstract

By implanting Zn þ ions into research-grade intentionally undoped ZnO single crystal for facilitating Zn interstitials (Zn i ) and O vacancies (V O ) which is revealed by precise X-Ray diffraction rocking curves, we observe an apparent broad red luminescence band with a nearly perfect Gaussian lineshape. This red luminescence band has the zero phonon line at $2.4 eV and shows distinctive lattice temperature dependence which is well interpreted with the configurational coordinate model. It also shows a low "kick out" thermal energy and small thermal quenching energy. A "selfactivated" optical transition between a shallow donor and the defect center of Zn i -V O complex or V Zn V O di-vacancies is proposed to be responsible for the red luminescence band. Accompanied with the optical transition, large lattice relaxation simultaneously occurs around the center, as indicated by the generation of multiphonons. V C 2014 AIP Publishing LLC.

Low temperature photoluminescence from disordered granular ZnO

“…Previous investigations on red luminescence (1.8-2.0 eV) in ZnO emphasized the role of V Zn clusters [35], I Zn [36], V O [37], combined effect of both V Zn and I Zn [5] and in general shallow donor electron transition to deep acceptor states [38]. In our view, low temperature red luminescence in ZnO, at least here in 500I and 800I samples, originates from V Zn -2V O type defects.…”

“…The qualitative understanding mentioned above has evolved several decades before, however, assignment of particular ZnO PL peak to specific defect site is still a matter of debate [4][5][6][7].…”

Room-temperature single-photon emission from zinc oxide nanoparticle defects and their in vitro photostable intrinsic fluorescence

“…Similarly, for yellow and orange-red emissions, there are many competing hypotheses, but the community has mainly attributed oxygen interstitials [34,38,39] as the primary candidate. More recently, red emission has been attributed to negatively charged zinc and positively charged oxygen vacancies within ZnO nanocrystals [40] and zinc interstitial-oxygen vacancy complexes or zinc-oxygen divacancies in ZnO single crystals [41]. Often, the contradictory results for ZnO defect emission may be attributed to the plethora of growth conditions that inevitably control what defects are introduced into the crystallographic structure of ZnO [4].…”

Luminescence of rare-earth ions and intrinsic defects in Gd2O3matrix

“…In other words, matrix Gd 3+ ions behave as extrinsic activators that act as energy donors. In different host lattices the nature of the self-activation centers has been related to the point distortions of lattice caused by deviations from stoichiometry [9,10]. In our case, the most possible intrinsic defects involved in absorption and luminescence processes are either interstitial Gd 3+ ions or Gd 3+ at normal lattice sites associated with other nearest point defects.…”