Low Temperature Electronic Properties of Electrospun PAN-Derived Carbon Nanofiber
Yu Wang, and Jorge J. Santiago-Aviles
Department of Electrical & Systems Engineering, University of Pennsylvania, US
Keywords: Conductivity, carbon fiber, electronic properties, low temperature
The possible sensor application of carbon nanofibers relies on the nanofibers' electronic transport. This paper fabricated carbon nanofibers using electrostatic deposition and vacuum pyrolysis techniques. Scanning electron microscope (SEM) and scanning probe microscopes (SPM) images show the diameter of the pyrolyzed fibers to be around 100nm. The scattering peaks centered around 1371 and 1588 cm-1 in Raman micro spectrum identifies the coexistence of disordered and graphitic carbons in the nanofiber. The in-plane graphitic crystallite size La was estimated to be around 2.5nm. . The resistance/conductance of carbon fibers was measured using the two probe method at 295K (room temperature), and the four probe method from 295K down to 15K. The semiconducting nature of the fiber is revealed by the thermal coefficient of resistance, i.e. the increase in conductivity ( ), with the increase of the temperature (T). The correlation between and T can be fitted either as: = 0+ 10 exp(-Eg1/kT)+ 20 exp(-Eg2/kT), with 0=8567 85 S/m, 10=21254 194 S/m, 20=13894 64 S/m; Eg1=(2.97 0.04) 10-2eV, Eg2=(3.14 0.19) 10-3eV, suggesting three mechanisms in the conductivity, or as =P1+P2ln(T)+P3T-0.5+P4P0.5, where P1=19092 1101S/m, P2=-2165 252S, P3=-34147 2121S K2, P4=1323 27S K-2, suggesting that weak localization of charge carriers, electron-electron interaction, and Kondo effect may still be significant in carbon nanofibers.
NSTI Nanotech 2003 Conference Technical Program Abstract