Two-dimensional carbon nanostructures and their electrical transport properties

Abstract

Being able to be made into zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) nanostructures, carbon provides unique opportunities that other materials lack. Although tremendous efforts have been devoted to the study of 0D and 1D nanocarbons, the work on 2D nanocarbons has been just started. In the last few years, we have developed a technique to grow vertically aligned 2D carbon structures on various types of substrates. In this paper, we review briefly the growth process and then focus on the electrical transport properties of 2D carbon nano-sheets using both normal metal and superconducting electrodes. In order to overcome the large topography of the 2D carbon samples, we have employed bottom electrodes patterned by e-beam lithography as the electrical contacts. The dI/dV (or dV/dI) curves of samples with different electrode spacings have been measured at different temperature and with different applied magnetic fields. The nonlinear transport and corresponding anomalous dI/dV versus bias curves at low temperature is accounted for by the contribution from charge density waves formed at edges or extended defects due to the enhancement of density of states at the Fermi level in these regions.