Project of the month, March 2009

Carbon Nanotube Based Molecular Electronics

Carbon nanotubes (CNTs) have been considered as a better alternative to metal electrodes in making molecular electronic devices. It takes the advantage of two distinct features of CNTs, namely the controllable nano-size and the ability to form strong covalent bonds with the molecule. The latter is particular attractive since it can in principle provide ample opportunities for making functional devices. The chemical bonding between CNTs and the molecule is complicated by the fact that the contact areas of CNTs are largely irregular as revealed by experimental studies. The presence of the defect and deformation can be used to alter the electrical properties and the electronic transport mechanical of CNTs, thus substantially modify molecular electronic structure of the molecule, hence to change the conductance of the device. However, the existing theoretical investigations have only considered ideal model systems, in which CNTs electrodes have perfect honeycomb arrangements on the side-wall with regular contacts. The designed ideal devices do not show any special functions.

In this project, we will combine molecular dynamics simulation with quantum mechanic calculations to study electron transport properties of carbon nanotube based molecular devices. The stretching process of CNT is simulated by molecular dynamics, as well as the possible bonding geometries. The quantum chemical calculations are used to optimize the geometry of most favorable structure, and Non-equilibrium Green’s function calculations are employed for calculating electron transport properties.

Figure 1: Mechanical single molecular switch with large ON/OFF ratio operated by simply pressing one of the electrodes vertically over a short distance (0.8nm).

This work is a part of molecular electronics project of XiaoFei Li.
If you have further questions, please contact me at xfli-at-theochem.kth.se.

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