The Tunable Luminescence from ZnO-Nanocrystal-Based Composites
G.N. Panin, A.N. Baranov, T.W. Kang
Dongguk University, KR
Keywords: nanocomposites, ZnO, Luminescence, nanocrystals, nanorods
Abstract:The luminescent properties of ZnO nanocrystals doped by different impurities and composites consisting of the ZnO nanocrystals and MgO matrix are investigated. XRD patterns and TEM data show that pure ZnO and ZnO-core in ZnO/MgO nanocomposites have a hexagonal phase with a typical size of 3 and 7 nm, respectively. The hexagonal ZnO and cubic MgO phases in the ZnO/MgO nanocomposites are thermally stable up to 500°C. The higher temperature annealing destroyed the two phase nanocomposite with formation of the solid solution and introduction of the radiative centers in green, yellow and red spectral regions. The nanocomposites based on ZnO core/MgO shell nanoheteroparticles showed an increase of the relative intensity of the green luminescence after annealing while suppressed PL green emission was observed from the nanocomposites consisting of the ZnO nanorods and MgO nanoparticles. The undoped and Mn, Al-doped ZnO nanocrystals show UV and green luminescence which is sensitive to the nanocomposite interface. The Fe- and Mg-doped nanocrystals show the red shifted luminescence which is less sensitive to the surface and interface band bending. The covering of ZnO nanorods by MgO particles leads to electron depletion of the ZnO surface and the formation of the surface band bending increasing portion of nonradiative states. The mechanism involved the formation of non-radiative and radiative states within and outside the depletion zone assumes an opportunity of an electric field control of green emission from the ZnO-based nanocomposite structures.