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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid-liquid interfaces; Scanning probe and other methods; Electronic structure theory; Spin-orbit interaction)

O 58.73: Poster

Mittwoch, 13. März 2013, 18:15–21:45, Poster B1

Electronic transport in carbon nanotubes: the role of water and long-range electrostatics — •Robert A. Bell¹, Arash Mostofi², and Mike Payne¹ — ¹TCM Group, Cavendish Laboratory, University of Cambridge, UK — ²Dept. of Materials & the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, UK

Understanding interactions between carbon nanotubes and environmental adsorbants is vital for the use of nanotube devices under ambient conditions. Previous theoretical studies have concluded water n-dopes the nanotube, providing a mechanism to increase conductivity.

In this work, we show that the use of short nanotube supercells in these calculations is inappropriate in the presence of long-range electrostatic interactions. Using large-scale DFT calculations with ONETEP, we study long (>60 Å) nanotube segments, and conclude that negligible charge is transferred between the water and the nanotube. Weak long-range charge-redistribution in the nanotube is observed, however, which is explained using a simple classical electrostatic model for the polarisation of the nanotube by the water dipole. Conclusions derived from local charge transfer methods such as Mulliken analyses are unable to capture this behaviour and are potentially misleading.

Electron transport calculations, using the Landauer-Büttiker approach, on large nanotube segments with many adsorbed water molecules show only weak scattering at the nanotube valence band edge. No evidence is observed to support an increase in conductivity.