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Surface modification of ZnO nanocombs was performed through a Ti plasma immersion ion implantation (PIII) with low bias voltages ranging from 0to5kV to quench surface-originated exciton emission. The ion energy dependent surface modification on ZnO was investigated using transmission electron microscopy and temperature-dependent photoluminescence (PL). The surface exciton (SX) was clearly identified for the as-grown sample at 4.5K, and complete quenching was observed for sample treated with 5kV PIII due to surface state passivation. The SX related surface states were located within 5nm in depth from the surface corresponding to the implantation depth of 5kV PIII. Room-temperature PL enhancement of these surface-modified ZnO nanocombs was observed and discussed. The results show that PIII can become a viable technique for nanostructure surface passivation.

Ge nanocrystals ͑nc-Ge͒ embedded in the gate oxide of the nonvolatile memory structure were synthesized by Ge ion implantation followed by thermal annealing at 800°C for various durations. Large changes in the structural and chemical properties of the Ge + -implanted oxide have been observed, and they have been found to possess a significant impact on the charge transfer in the oxide layer. The distribution and concentration of the nc-Ge and dissolved Ge atoms which serve as both the charge storage and transfer sites in the oxide are affected by the annealing. Two charge transfer mechanisms, i.e., the lateral charge diffusion along the Ge-distributed layer and the charge leakage from the charge storage sites to the Si substrate via the charge transfer sites, have been identified based on the charge retention behaviors. Both mechanisms are enhanced by the annealing as a result of the change in the distribution and concentration of the charge transfer sites.