Low temperature transport of a charge transfer complex nanowire grown with an electric field from the vapour phase

Abstract

Suspended Cu:TCNQ (Cu–tetracyanoquinodimethane) nanowires connecting two electrodes (∼1.0 µm gap) have been grown laterally from the vapour phase with and without the application of an external electric field between the electrodes during growth. The temperature and bias dependent conductance of these bridged nanowires have been investigated down to 40 K. It has been found that when the nanowires are grown in an electric field, their conductance is enhanced significantly. The nanowires show a strong non-linear conductance beyond a threshold bias along with a linear conductance at low bias. Below 100 K, the bias dependent non-linear conductance with a threshold can be fitted to a modified Zener tunneling model for charge density wave transport for both types of nanowires, raising the possibility of the onset of a charge density wave type of transport in the Cu:TCNQ nanowires. It has been proposed that the enhancement of the conductance in the Cu:TCNQ nanowires when growth is performed in the presence of an electric field, occurs due to a better charge transfer as well as more ordered arrangements of the TCNQ stacks during growth, which is enabled by the strongly anisotropic polarizability of the TCNQ moiety. This also modifies the parameters related to the non-linear conductance, including the threshold value.