Optical properties of ZnO and MgZnO nanocrystals below and at the phase separation range

This paper presents studies of the optical properties of MgxZn1−xO nanocrystals below and at the phase transition range where the solubility is limited. For the nanocrystals of Mg composition 0%–30%, the samples were found to consist of the wurtzite structure and exhibited band edge absorption as well as photoluminescence (PL) blueshift of ∼0.25 eV. The cold temperature PL of the ZnO nanocrystals exhibits the A-exciton and the bound exciton with values similar to that of the bulk ZnO reference sample. In addition, the PL of the ZnO nanocrystals was found to be dominated by an emission, referred to as the e-PL, at ∼3.32 eV that is ∼56 meV below the A-exciton. The characteristics of the e-PL agree well with model calculations of an emission that involves a transition of conduction-band electrons to acceptorlike states having an acceptor binding energy of ∼116 meV. The room temperature PL exhibited a strong exciton component, which is convoluted with the e-PL. The PL line shapes of the MgxZn1−xO samples of M...

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