Dissertations

Shastun V.

23.06.2014

Energy spectra and electrical properties of carbon nanotubes doped with N and Cr.
01.04.07 – solid state physics
Doctor of Philosophy degree (Candidate of science in Physics and Mathematics)

The thesis is devoted to the creation of the method for calculation of energy spectrum and electrical properties of low-dimensional systems with impurities.
We have studied based on the tight-binding model electronic structure, free energy and spin-dependent transport of carbon nanotubes doped with atoms N and Cr.
Based on a free energy minimum geometric optimization performed for the crystal structure of carbon nanotubes doped with nitrogen and mixed with chromium. It was found that nitrogen atoms replace carbon atoms and are randomly located in the lattice sites. Chromium atoms randomly located on the surface of carbon nanotubes across centers of hexagons formed with carbon atoms.
We have studied the influence of external magnetic field on electron transport and localized magnetic moments. The nature of the spin-dependent transport in carbon nanotubes and graphene doped with chromium was determined. It was found that the spin-dependent transport is determined by the difference of the partial densities of states for different spin orientations relative to the external magnetic field at the Fermi level and the relaxation of electronic states. It was found that the magnitude of the spin polarization of electron transport increases with the impurity concentration of chromium and increasing the value of the external magnetic field.

Keywords: electronic structure, spin-dependent transport, localized magnetic moments of the Green function, graphene.

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