We have investigated the energy loss of hot electrons in metallic graphene by means of GHz noise thermometry at liquid helium temperature. We observe the electronic temperature T ∝ V at low bias in agreement with the heat diffusion to the leads described by the Wiedemann-Franz law. We report on T ∝ √V behavior at high bias, which corresponds to a T(4) dependence of the cooling power. This is the signature of a 2D acoustic phonon cooling mechanism. From a heat equation analysis of the two regimes we extract accurate values of the electron-acoustic phonon coupling constant Σ in monolayer graphene. Our measurements point to an important effect of lattice disorder in the reduction of Σ, not yet considered by theory. Moreover, our study provides a strong and firm support to the rising field of graphene bolometric detectors.

In situ Raman measurements were used to investigate the kinetics and the self-deactivation of the growth of single-walled carbon nanotubes during catalytic chemical vapor deposition. The kinetics appear controlled by the mass-transport of the gaseous precursor at low precursor pressure and high temperature and by the catalytic decomposition of the precursor at high precursor pressure and low temperature. The initial growth rate and the lifetime display inversely correlated evolutions with the growth parameters. In addition, we measured the activation energy for the healing of defects during the growth and discuss it in comparison to the apparent activation energies measured for the initial growth rate and the lifetime. Our results support that the healing of the edge defects controls both the crystalline order and the growth lifetime.

From combined Raman spectroscopy and electron diffraction studies on several freestanding single-walled carbon nanotubes (SWNTs), we define Raman criteria which correlate the main features of the Raman spectrum (radial breathing mode and G modes) and the optical transition energies with the structure of the SWNT under investigation. On this basis, we discuss the possibilities to determine the (n,m) indices of an individual SWNT from a single wavelength Raman experiment. We show the efficiency of this approach in assigning the (n,m) structure of different individual nanotubes including all types of achiral SWNTs. Finally, the limits and the accuracy of the method are discussed