KEYWORDS: Single walled carbon nanotubes, Carbon nanotubes, Terahertz radiation, Near field, Near field scanning optical microscopy, Scattering, Electromagnetism, Optical microscopy, Molecules, Near field optics
The use of carbon nanotubes as optical probes for scanning near-field optical microscopy requires an understanding of their near-field response. As a first step in this direction, we investigated the lateral resolution of a carbon nanotube tip with respect to an ideal electric dipole representing an elementary detected object. A Fredholm integral equation of the first kind was formulated for the surface electric current density induced on a single-wall carbon nanotube (SWNT) by the electromagnetic field due to an arbitrarily oriented electric dipole located outside the SWNT. The response of the SWNT to the near field of a source electric dipole can be classified into two types, because surface-wave propagation occurs with (i) low damping at frequencies less than ~ 200-250 THz and (ii) high damping at higher frequencies. The interaction between the source electric dipole and the SWNT depends critically on their relative location and relative orientation, and shows evidence of the geometrical resonances of the SWNT in the low-frequency regime. These resonances disappear when the relaxation time of the SWNT is sufficiently low. The far-field radiation intensity is much higher when the source electric dipole is placed near an edge of SWNT than at the centroid of the SWNT. The use of an SWNT tip in scattering-type scanning near-field optical microscopy can deliver a resolution less than ~ 20 nm. Moreover, our study shows that the relative orientation and distance between the SWNT and the nanoscale dipole source can be detected.
The novel thermal conductance mechanism, theoretically predicted and experimentally measured in nanotube
field-effect transistors (FET), is discussed with respect to the power dissipation problem of modern carbon-based
electronics. Such an effect is due to the near-field coupling of the charge carriers in the transistor channel with
the local electric field of the surface electromagnetic modes. The coupling leads to a quantum electrodynamic
(QED) energy exchange between the hot electrons in FET channel and the optical polar phonon bath being in
thermal equilibrium with the substrate. For an example of a NT on silica, this QED coupling mechanism is
shown to exceed significantly the interface Kapitza conductance, that is, the classical phonon heat transport.
The QED thermal conductance is proposed to play dominant role in the energy dissipation in nanoelectronics
with a hetero-interface between the device channel and the polar substrate.
The physics of operation of nanotube NEMS devices is reviewed. Special attention is paid to non-classical effects,
rarely described in MEMS analysis, such as van derWaals/Casimir interactions, quantum effects in electrostatics,
atomistic parameterization of elasticity. As an example of a breakdown of a classical MEMS theory, the NEMS
scaling limitation is derived in a lump model taking into account van der Waals/Casimir attraction.
Breaking of the symmetry of a single-wall carbon nanotube in the field of a helical wrap of ionized single-stranded DNA
is investigated. For a non-chiral tube, the helical perturbation generates "natural" optical activity in the DNA-nanotube
complex. The one-electron absorption spectrum for light polarized across the tube is sensitive to the band structure
modulation due to the wrapping. Lifting of optical selection rules results in new optical transitions and circular
dichroism of the complex. These optical effects are predicted to serve as qualitative tools to directly identify the DNA
The optical dichroism which appears in the nanotube-DNA hybrid is studied within a phenomenological approach. Naturally non-chiral nanotubes may acquire a chiral optical response when wrapped by the DNA helix. The hybrids of the DNA and the metallic nanotubes are discussed in conjunction with the possible gap opening and the subsequent arising of a pair of van Hove singularities close to the Fermi point. Polarized light absorption experiments are proposed to find the predicted effect.
The paper reviews current theoretical methods to study quasi-electrostatic phenomena in single-wall nanotube systems. Several models are presented to demonstrate importance of selfconsistent calculation of the electric fields for electronic device applications. The quantum mechanical formalism of the dielectric function is chosen to obtain the selfconsistent solution. It gives a unified approach to calculate exciton binding energy, to obtain transverse and longitudinal polarization in the nanotube, to study symmetry breaking and band gap engineering in electric fields, and to perform modelling of ballistic transport in a light-operated switches.