Study Of Fabrication And Optical Properties Of Zinc Oxide/Metal Composite Nanostructures

Recently, widespread attention has been paid to the research of effective emission enhancement of metal/semiconductor composite structures. Among many semiconductors, ZnO is regarded as one of the most promising candidates for ultraviolet photo-electronic materials and devices due to its wide band gap (3.37 eV) and high exciton binding energy (60 meV). In general conditions, a large portion of excited charge carriers are trapped in the defect energy states of ZnO, which reduces the UV emission efficiency. Therefore, it is expected that the ultraviolet emission of ZnO can be inhanced by the fabrication of approporiate composite nanostrctures. Besides, the surface enhanced Raman scattering (SERS) spectrum technique plays an important role in the trace molecular detection. One of the key factors of this technique is the fabrication of reliable SERS active substrate. ZnO nanostructures have many advantages, such as large specific surface area, high isoelectric point, and good biological compatibility. This make the ZnO/metal composite nanostructures ideal candidates for the SERS substrates. Based on the above discussion, the main research works are carried out as follows:1. ZnO nanorods are fabricated by chemical vapor deposition method. ZnO nanorods are well aligned and present uniform morphology and diameter by controlling the ratio of raw materials and atmosphere conditions. Au nanoparticles are decorated on the surface of ZnO nanorods by a hydrothermal method. It is found that the two-photon excitation threshold of Au-decorated ZnO sample is much lower than that of the as-grown sample under the excitation of 520 nm. Under the same excitation power, the UV emission intensity is strongly enhanced after the Au NPs are assembled on the surfaces of ZnO nanorods.2. Monodispersed ZnO microflowers are fabricated by a vapor phase transport method and Au nanoparticles (NPs) are directly decorated on the surface of the ZnO microflowers. The micro-photoluminescence of a single ZnO microflower demonstrates that the near band-edge emission is tremendously enhanced while the defect-related emission is completely suppressed after Au decoration. The average enhancement factor reaches up to 65 fold. Furthermore, The enhanced F-P lasing from a single ZnO sample is also realized.3. ZnO films and nonorods arrays are fabricated by magnetron sputtering and hydrothermal methods. Au nanoparticles are decorated on the surfaces of Si, ZnO film and ZnO nanorods, respectively. The three sets of substrates are used to detect the Raman signals of R6G. The results demonstrate that the substrate of Au decorated ZnO nanorods achieves the best enhancement effect.