Design, Fabrication, and Characterization of Three-Dimensional Single-Walled Carbon Nanotube Assembly and Applications As Thermal Sensors

We present the design, fabrication, and characterization of vertical assembly of 3-D single-walled carbon nanotubes (SWNTs) thermal sensors. Carbon nanotubes (CNT) were deposited utilizing dielectrophoretic (DEP) assembly technique with a 98.7% yield. The scanning electron micrograph images revealed that by adjusting the height of the 3-D microelectrodes and the overlap between them allows control over bundle size, number of bundles, and effective length of the sensing elements. The two-terminal resistance of the 3-D devices was reduced by 20% on average from their initial values after the thermal annealing process. The 3-D SWNT thermal sensors were next characterized and a higher temperature coefficient of resistance (TCR) was measured compared to the previously reported DEP aligned CNT-based thermal sensors. The TCR of the single-electrode thermal sensor ranged from -0.157%/°C to -0.232%/°C, whereas the TCR of the multielectrode sensor varied from -0.327%/°C to -0.778%/°C measured during the heating cycle. The thermal sensitivities of these 3-D devices were also measured during cooling where the obtained TCR was close to the values obtained during the heating cycle.