氧化鋅/銀奈米線/氧化鋅複合電極的兆赫光譜導電性改善

Abstract

In this thesis, we fabricated transparent conductive electrode based on silver nanowires (AgNWs) and ZnO bilayers (ZnO/AgNW/ZnO). Percolative AgNW networks were embedded between either single-crystalline or polycrystalline ZnO (33 nm) bilayers in order to investigate the dependence of effective electrical conductivity on the interface between two materials. Terahertz time-domain spectroscopy (THz-TDS), which is an optical and non-contact method, was employed to measure the complex THz conductivity and dielectric responses of the ZnO/AgNW/ZnO samples with different AgNW density, but near the threshold density of percolational transition. In the THz spectroscopy, the percolation threshold corresponds to a critical AgNW density at which a crossover from Drude to non-Drude behavior occurs. The results of both THz analysis and contact-based conductivity measurement show that AgNW electrode with single-crystalline ZnO underlayer has higher conductivity than that with polycralline ZnO layer. ZnO overlayer covering AgNW/ZnO film improves the contact at NW junctions and increases the conductivity, but this improvement is less sensitive to the cryalline quality of ZnO overlayer. We also compared the thermal stability of ZnO/AgNW/ZnO films with AgNW/graphene overlayer annealed at 200 oC by THz measurement, and found that low thermal conductivity of ZnO leads to the melting of NWs at lower temperature than the typical melting temperature of AgNW.

In this thesis, we fabricated transparent conductive electrode based on silver nanowires (AgNWs) and ZnO bilayers (ZnO/AgNW/ZnO). Percolative AgNW networks were embedded between either single-crystalline or polycrystalline ZnO (33 nm) bilayers in order to investigate the dependence of effective electrical conductivity on the interface between two materials. Terahertz time-domain spectroscopy (THz-TDS), which is an optical and non-contact method, was employed to measure the complex THz conductivity and dielectric responses of the ZnO/AgNW/ZnO samples with different AgNW density, but near the threshold density of percolational transition. In the THz spectroscopy, the percolation threshold corresponds to a critical AgNW density at which a crossover from Drude to non-Drude behavior occurs. The results of both THz analysis and contact-based conductivity measurement show that AgNW electrode with single-crystalline ZnO underlayer has higher conductivity than that with polycralline ZnO layer. ZnO overlayer covering AgNW/ZnO film improves the contact at NW junctions and increases the conductivity, but this improvement is less sensitive to the cryalline quality of ZnO overlayer. We also compared the thermal stability of ZnO/AgNW/ZnO films with AgNW/graphene overlayer annealed at 200 oC by THz measurement, and found that low thermal conductivity of ZnO leads to the melting of NWs at lower temperature than the typical melting temperature of AgNW.