Electrical and Thermal Interface Conductance of Carbon Nanotubes Grown under Direct Current Bias Voltage

The electrical resistance of individual multiwalled carbon nanotubes and the thermal interface resistance of nanotube arrays are investigated as functions of dc bias voltage used during growth. Nanotubes were grown from Fe2O3 nanoparticles supported on Ti/SiO2/Si substrates by microwave plasma chemical vapor deposition (MPCVD) under dc bias voltages of -200, -100, 0, +100, and +200 V. Electrical resistances of individual nanotubes were obtained from I-V measurements of randomly selected nanotubes, while thermal interface resistances of nanotube arrays were measured using a photoacoustic technique. The study reveals that individual nanotubes and nanotube arrays grown under positive dc bias voltage (+200 V) show significant increases in their electrical and thermal interface conductance, respectively. The nanotubes have been further characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electron microscopy in order to account for the marked differences in electrical and thermal interface conductance.