Electronic structure of embedded carbon nanotubes

The electronic structure of single-wall carbon nanotubes embedded in a crystal matrix is calculated by means of a linear-augmented cylindrical wave method. A delocalization of the nanotube electrons into the matrix region results in a strong band-structure perturbation. In the case of armchair nanotubes, the delocalization is responsible for a high energy shift of the sigma states and growth of the electron density of states at the Fermi level. For the semiconducting nanotubes, it causes a decay of the minimum energy gap and the formation of a metallic state. The effect of embedded nanotube metallization correlates with the transport properties of devices with nanotubes encapsulated in a semiconductor crystal.