Characterization of carbon nanotubes by THz time-domain spectroscopy

Using an optoelectronic THz beam system for THz time-domain spectroscopy (THz-TDS), we have measured the absorption and dispersion of singlewalled and multiwalied carbon nanotubes (CNTs) from low frequencies to 3 THz. In contrast tc the metals and semiconductors, characterizations of CNTs by a simple Hall measurement due to large conductivity. However, in our non-contact THz-TDS technique, the power absorption, index of refraction, and complex conductance were obtained over the frequency range. We find that the real conductivity increases with increasing THz frequency. The measured real conductivity does not follow the simple Drude theory and is not comparable with normal metals and semiconductors.