MODULATION OF THE ELECTRINIC STRUCTURE OF ULTRA-SHORT CARBON NANOTUBES (0,9) DOPED BY ALKALIC METALS

Abstract

The main task for modern spintronics is to find materials with high spin polarization that enable spin transport. Carbon nanomaterials are under special focus, including ultra-short carbon nanotubes (us-CNTs) which are thermodynamically stable and have high spin polarization. Synthesis methods for us-CNTs with a narrow distribution of the tube length and chirality have recently been developed.

The paper describes a numerical simulation experiment that was carried out by means of the method based on density functional theory. Its goal was to calculate the main electron structure parameters of alkali-metal doped us-CNTs to determine the conditions of intrinsic spin polarization.

It was established that in a close interval the 3k-rule does not work for metal tubes (0,9). There is a non-zero gap between the frontier molecular orbitals and the tube acts as a semiconductor. The gap between the highest occupied and the lowest unoccupied molecular orbitals depends on electron spin at the triplet state, thus the conductivity is spin-dependent, which makes it possible to use us-CNTs to construct transport devices. The energy gap decreases with an increase in tube length.

The controlled alkali metal doping modulates the energy gap that leads to the increase in conductivity and spin polarization in case of anion complexes.

Thus, the paper describes a technological way to modify the properties of us-CNTs to create functional spintronic devices.

ACKNOWLEDGEMENTS

The reported study was supported by the Russian Foundation for Basic Research (project No.6-32-00926 mol_a).