Zinc oxide nanoparticles fabricated by ion implantation and thermal oxidation and the optical properties

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This study consists of three sub-themes, i.e., (1) Formation processes of ZnO nanoparticles (NPs), (2) High density excitation effects on ZnO NPs, and (3) an attempt for size control of ZnO NPs.(1) Formation processes of ZnO NPsZn NPs were formed in silica glass samples by Zn+ ion implantation of 60 keV. After then the samples including Zn NPs were annealed in oxygen gas to oxidize the Zn NPs to ZnO NPs. The transformation from Zn NPs to ZnO NPs was evaluated by. UV-Vis optical absorption spectroscopy, glancing angle incident x-ray diffraction, cross-sectional transmission electron microscopy, Rutherford backscattering spectrometry. One of the striking results is that Zn NPs formed inside the silica glass move toward the surface of the glass and transform to ZnO NPs on the surface of the glass.(2) High density excitation effects on ZnO NPsFirst, photoluminescence (PL) measurements of ZnO NPs using a time-resolved PL measurement system using a nitrogen laser was carried out, but the sensitivity was too low to detect PL of our samples. We have built a new measurement system using YAG laser and ICCD detector, and succeeded in the observation of PL spectra under high-density pulsed laser excitation. The exciton PL showed a saturated excitation intensity dependence at room temperature.(3) An attempt for size control of ZnO NPs.Size control of Zn and ZnO NPs by changing the fluence was examined. In as-implanted state, the average size of Zn NPs increases with the fluence between 5 and 10×10^<16>ions/cm2. Above 10×10^<16>ions/cm2, the average size showed a saturation behavior due to surface sputtering. After the oxidation annealing, the samples implanted to 2×10^<16>ions/cm2 or less mainly transformed to Zn_2SiO_4 phase instead of ZnO NPs.