Terahertz-infrared conductivity of plasma-treated of CNT-based macroscale films

Time-domain terahertz and infrared Fourier-transform spectroscopy techniques are used to study the temperature-dependent conductivity spectra of free-standing macroscale films composed of disordered single-walled carbon nanotubes. Comparative experiments are performed on films composed of nanotubes a) treated with oxygen plasma and b) having different lengths. We observe and analyze transformation of the terahertz conductivity of the films from metal-type to semiconductor-like. We trace evolution of the terahertz conductivity peak during the change of the temperature and the length of nanotubes. In films treated with oxygen plasma, the temperature dependence of the terahertz conductivity of only the semiconductor-type was observed and it decreased with exposure time.