I-Tan Lin1, Jia-Ming Liu1,*, Kai-Yao Shi2, Pei-Shan Tseng2, Kuang-Hsiung Wu2, Chih-Wei Luo2, and Lain-Jong Li3
1Electrical Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, USA
2Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
1Electrical Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, USA
2Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
Received 8 November 2012; published 27 December 2012
The optical conductivity of monolayer and multilayer graphene in the terahertz spectral region is experimentally measured using terahertz time-domain spectroscopy. The stacking arrangement and the misorientation angle of each sample are determined by Raman spectroscopy. The chemical potential of each sample is measured using ultrafast midinfrared pump-probe spectroscopy to be 63 or 64 meV for all samples. The intraband scattering rate can be obtained by fitting the measured data with theoretical models. Other physical parameters, including carrier density, dc conductivity, and carrier mobility, of each sample can also be deduced from the theoretical fitting. The fitting results show the existence of misoriented or AA-stacked layers with an interaction energy of α1=217 meV in our multilayer samples. Here we show that the scattering rate strongly depends on the stacking arrangement of the sample. High scattering rates and high optical conductivity are associated with AA-stacked samples, while lower ones are associated with misoriented multilayer graphene. This implies that the THz optoelectronic properties of multilayer graphene can be tuned by purposefully misorienting layers or employing different stacking schemes.
©2012 American Physical Society
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