A temperature dependent (10K-290K) photoluminescence (PL) study for two differently prepared ZnO thin films (as-grown and O-plasma treated) is presented. Four characteristic peaks were identified for both samples: (i) neutral donor-bound excitons (<TEX>$D^oX$</TEX>), (ii) two electron satellites (TES), (iii) phonon replica of <TEX>$D^oX$</TEX> (<TEX>$D^oX$</TEX>-1LO), and (iv) donor-acceptor pair transition (DAP). As the sample temperature increased, <TEX>$D^oX$</TEX>-1LO and DAP transitions became indistinct. This was accompanied by newly-rising emission of free electron-acceptor transitions (e, <TEX>$A^o$</TEX>). The spectral evolution with temperature for as-grown samples also showed the optical emission from free excitons, which became dominant at higher temperatures. Some features related to O-plasma were identified in PL spectra: (i) different positions of TES transitions (28meV lower than <TEX>$D^oX$</TEX> for as-grown samples and 35meV for O-plasma treated samples), (ii) the decrease of spectral intensity in both emissions of <TEX>$D^oX$</TEX> and DAP after O-plasma treatment, and (iii) no noticeable transition from free excitons after the O-plasma treatment.

© 2013 Optical Society of Korea

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