以兆赫輻射時域解析頻譜研究金奈米粒子石墨烯複合物的電磁特性

Abstract

本論文以兆赫輻射時域解析頻譜進行金奈米粒子單層石墨烯複合物的兆赫頻譜電磁特性研究。石墨烯因其優異的性質成為發展高速光電元件具有相當潛力的熱門材料。本研究探討以化學氣相沉積法成長之單層石墨烯在以金奈米粒子改質後於兆赫波段的響應，並進行電磁特性分析。先利用兆赫輻射時域解析頻譜得到光學片電導率，接著利用居得─史密斯模型將實驗得到之光學片電導率進行擬合，而獲得材料直流電導率以及載子散射率，藉由擬合得到之參數計算材料之載子濃度、費米能量以及載子遷移率，討論經金奈米粒子改質後對單層石墨烯於兆赫波段下的特性差異。

In this study, terahertz time-domain spectroscopy (THz-TDS) has been used to characterize the THz electromagnetic properties of gold nanoparticles (Au-NPs)-graphene composite. Due to the extraordinary properties, graphene possesses considerable potential as a material for ultrahigh-speed THz optoelectronics devices. In this work, we measure the electromagnetic properties of chemical vapor deposition-grown single-layer graphene decorated by Au-NPs. The optical sheet conductivity is obtained from the measurements of THz-TDS. The experimental data is fitted with the Drude-Smith model in order to extract the dc conductivity and scattering rate. The extracted physical parameters are then used to evaluate the carrier concentration, Fermi energy and mobility of each sample. We find that the sheet conductivity in the THz range enhances as concentration of Au-NPs increases, which is consistent with the theoretical prediction. The induced hole carriers in graphene by decorating Au-NPs can be tuned from 1012 cm-2 to 1013 cm-2, the corresponding Fermi energy is shifted from -140 meV to -479 meV. The changes of scattering rate and mobility with varies carrier concentrations also have been explained.