利用脈衝雷射蒸鍍法製備碲硒化鉍薄膜與其兆赫波時域頻譜研究

Abstract

在本論文中，我們利用脈衝雷射蒸鍍法將不同成份比例碲硒化鉍薄膜成功長在藍寶石(0001)的基板上，並藉由改變一系列的基板溫度來使薄膜達到最佳化條件，而晶格結構與薄膜品質我們就利用XRD、Raman來量測。接著利用霍爾儀器來量測薄膜的載子濃度和遷移率，並用兆赫波時域頻譜來研究其在此頻段下的電磁特性。利用量測結果與理論分析可獲得與頻率相關之薄膜材料的複數折射率，並進一步求得材料之介電係數、光學電導率，再透過Drude-Lorentz模型來進行數學擬合，可以得到材料的電漿頻率以及散射率。本文將討論對於所觀察到的不同成份比例碲硒化鉍薄膜在THz頻段下的響應進行討論。

In this report, we investigate the growth of the Bi-based topological insulator material on Al2O3(0 0 0 1) substrate by pulsed laser deposition (PLD) with various temperature, the structure and the quality were studied by X-ray diffraction(XRD) and Raman spectroscopy. The XRD results show the highly c-axis orientation of Bi2(Te1-xSex)3 thin films. And the Raman spectrum results show the frequency shift of phonon mode. The electromagnetic properties of Bi2(Te1-xSex)3 thin films at THz frequency have been studied by Terahertz Time-Domain-Spectroscopy (THz-TDS). The frequency dependence of the complex index of refraction, dielectric function and conductivity can be determined from the complex transmittance and Fresnel equation. We can observe that the carrier concentration and the optical conductivity increase for Se doping.