利用脈衝雷射蒸鍍法製備碲化鉍薄膜與其變溫兆赫波時域頻譜研究

Abstract

在本論文中，我們將利用脈衝雷射蒸鍍法調控溫度、壓力與脈衝能量將最佳化的碲化鉍薄膜成功的長在藍寶石(0001)基板上。隨後利用XRD、Raman、EDS來量測碲化鉍的晶格結構、薄膜品質與碲、鉍間之組成比例。並且用可變溫兆赫波時域頻譜來研究此薄膜在兆赫波頻段下的電磁特性。利用量測數據與理論分析可獲得此薄膜材料在各種不同溫度之下的光學電導率，再透過Drude-Lorentz、Drude-Fano模型來進行數學擬合，並可以得到碲化鉍薄膜之聲子模態振動頻率、電漿頻率以及散射率。最後我們會將兆赫波輻射經過不同溫度下的碲化鉍薄膜所得到的光電常數與溫度之間的關係以及低溫區間電子-聲子耦合現象進行討論與分析。

In this work, we have prepared Bi2Te3 thinfilm grown on sapphire (Al2O3) (0001) substrates by pulsed laser deposition (PLD) with optimized deposition temperature, pressure and pulse energy. The Bi2Te3 thinfilm quality, structure and Bi/Te ratio analyzed by X-ray diffraction (XRD), Raman spectroscopy and Energy dispersive spectrometer (EDS). Moreover, we have used temperature dependent time-domain terahertz spectroscopy to investigate the low-frequency complex conductivity in Bi2Te3 thinfilm at different temperature. The temperature dependent terahertz conductivity of optimized Bi2Te3 thinfilm can be fitted with Durde-Lorentz and Drude-Fano model. Finally, we can observe that the relationship between optical constants and temperature, including the phonon oscillator frequency, plasma frequency and scattering rate. In addition, the electron-phonon couple effect was also found at the low-temperature region.