Charge Transport in Mesoscopic Carbon Network Structures
V. Ksenevich
1
, J. Galibert
2
, V. Samuilov
1,2,3
, Y.-S. Seo
3
, J. Sokolov
3
, M. Rafailovich
3
1
Department of Physics, State University of Belarus, 220080, Minsk, Belarus
2
Laboratoire National des Champs Magnetiques Pulses, F-31432 Toulouse CEDEX 4, France
3
Department of Materials Science, SUNY at Stony Brook, Stony Brook, NY 11794, USA
ABSTRACT
The charge transport and quantum interference effects in low-dimensional mesoscopic carbon
networks prepared using self-assembling were investigated.
The mechanism of conduction in low-dimensional carbon networks was found to depend on the
annealing temperature of the nitrocellulose precursor. The charge transport mechanism for
carbon networks obtained at T
ann
=750
0
C was found to be the hopping conductivity in the entire
investigated temperature range. The Coulomb gap near the Fermi level in the density of states
was observed in the investigated carbon networks. The width of the Coulomb gap was found to
be decreased with the annealing temperature of the carbon structures. The crossover from the
strong localization to the weak localization regime of the charge transport in the carbon
structures, obtained at T
ann
=950
0
C and T
ann
=1150
0
C, was observed in the temperature range
T>100 K and T>20 K, respectively.
INTRODUCTION
High temperature treatment of polymer precursors in vacuum results in different carbon
structures synthesis, like carbon fibers [1-3], carbon-black polymer composites [4,5], porous
aerogels [1,6] and low dimensional carbon networks [7,8]. These disordered carbon matrixes
have been used as model materials for electronic transport phenomena investigation dependently
on the annealing temperature, which was found to determine the degree of disorder. As a result
different quantum phenomena can be observed: strong localization, hopping conductivity,
quantum interference, weak localization, metal-insulator (MI) transition.
These carbon materials could be considered as nanostructured materials with different internal
morphology. We have developed a simple approach of self-organized fabrication of two
dimensional mesoscopic networks with the feature size down to 50 nm and the size of the cells
of the order of 500 nm. Two dimensional mesoscopic network-like carbon structures were
produced by high temperature annealing of nitrocellulose precursors [8].
EXPERIMENTAL DETAILS
The technique is based on the self-organized patterning in a thin layer of complex liquid -
diluted nitrocellulose solution (1% nitrocellulose in amyl acetate with ethyl alcohol as a solvent)
in the presence of humid atmosphere. The sub-micron sized water droplets were trapped at the
surface and self assemble in regular aggregates. The polymer was found to precipitate at the
water-polymer solution interface, forming a layer encapsulating the droplets and preventing their
coalescence. After the evaporation of the solvent the resulting networks were transferred onto
Mat. Res. Soc. Symp. Proc. Vol. 705 © 2002 Materials Research Society
Y8.9.1