Whelan Patrick R, Shen Qian, Luo Da, Wang Meihui, Ruoff Rodney S, Jepsen Peter U, Bøggild Peter, Zhou Binbin
Opt Express. 2020 Sep 28;28(20):28819-28830. doi: 10.1364/OE.402447.
We present a reference-free method to determine electrical parameters of thin conducting films by steady state transmission-mode terahertz time-domain spectroscopy (THz-TDS). We demonstrate that the frequency-dependent AC conductivity of graphene can be acquired by comparing the directly transmitted THz pulse with a transient internal reflection within the substrate which avoids the need for a standard reference scan. The DC sheet conductivity, scattering time, carrier density, mobility, and Fermi velocity of graphene are retrieved subsequently by fitting the AC conductivity with the Drude model. This reference-free method was investigated with two complementary THz setups: one commercial fibre-coupled THz spectrometer with fast scanning rate (0.2-1.5 THz) and one air-plasma based ultra-broadband THz spectrometer for greatly extended frequency range (2-10 THz). Certain propagation correction terms for more accurate retrieval of electrical parameters are discussed.
我们提出了一种通过稳态传输模式太赫兹时域光谱（THz-TDS）来确定薄导电膜电学参数的无参考方法。我们证明，通过将直接传输的太赫兹脉冲与衬底内的瞬态内反射进行比较，可以获得石墨烯的频率相关交流电导率，从而无需进行标准参考扫描。随后，通过用德鲁德模型拟合交流电导率来反演石墨烯的直流面电导率、散射时间、载流子密度、迁移率和费米速度。使用两种互补的太赫兹装置对这种无参考方法进行了研究：一种是具有快速扫描速率（0.2 - 1.5太赫兹）的商用光纤耦合太赫兹光谱仪，另一种是基于空气等离子体的超宽带太赫兹光谱仪，用于大幅扩展频率范围（2 - 10太赫兹）。讨论了用于更准确反演电学参数的某些传播校正项。
