Liwei Chen

Publications (2)3.48 Total impact

• Source

  Available from: Binh Duong

  Article: Demetalization of single-walled carbon nanotube thin films with microwave irradiation

  Lu Wang, Yao Xiong, Ziran Wu, Binh Duong, Supapan Seraphin, Hao Xin, Liwei Chen
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  ABSTRACT: The microwave irradiation effects on purified HiPCO and CoMoCat single-walled carbon nanotube (SWNT) thin films are investigated. The surface conductivities of the SWNT films are extracted from the measured THz transmission coefficients to provide a direct indication of the metallic content in the films. The observed drastic conductivity decrease indicates a significant metallic content reduction after the microwave irradiation. Two different laser excitations are applied for Raman spectroscopy to reveal the response of different nanotube species. The Raman spectra of both HiPCO and CoMoCat thin films confirm the decrease of metallic carbon nanotubes. The observed microwave-induced effects may potentially lead to a convenient scheme for demetalization of single-walled carbon nanotube mixtures.
  Applied Physics A 04/2012; 102(2):401-406. · 1.63 Impact Factor
• Source

  Available from: sinano.ac.cn

  Article: Terahertz Characterization of Single-Walled Carbon Nanotube and Graphene On-Substrate Thin Films

  Min Liang, Ziran Wu, Liwei Chen, Li Song, P. Ajayan, Hao Xin
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  ABSTRACT: In this paper, single-walled carbon nanotube (SWNT) thin films with thicknesses on the order of hundreds nanometers on glass substrates and a graphene thin film (2-3 layers) on a glass substrate are characterized via terahertz time-domain spectroscopy. The substrate permittivity is first characterized. The thin film is then treated as a surface boundary condition between the substrate and air. Using the uniform field approximation, the surface conductivities of these films are extracted. To improve accuracy, precise thickness of the sample substrate is calculated through an iteration process in both dielectric constant extraction and surface conductivity extraction. Uncertainty analysis of the measured thin-film properties is performed. The SWNT results show consistent surface conductivities for samples on different substrates and with different film thicknesses. The measured graphene terahertz conductivity is comparable to the values reported in the literature at dc and optical frequency. This characterization method has been successfully applied as a means to evaluate metallic content of SWNT samples to verify a metallic SWNT removing process using high-power microwave irradiation.
  IEEE Transactions on Microwave Theory and Techniques 11/2011; · 1.85 Impact Factor