We analyze the electrostatic interactions between a single graphene layer and a SiO2 susbtrate, and other materials which may exist in its environment. We obtain that the leading effects arise from the polar modes at the SiO2 surface, and water molecules, which may form layers between the graphene sheet and the substrate. The strength of the interactions implies that graphene is pinned to the substrate at distances greater than a few lattice spacings. The implications for graphene nanoelectromechanical systems, and for the interaction between graphene and a STM tip are also considered.

Modifying and extending recent ideas 1 , a theoretical framework to describe dissipation processes in the surfaces of vibrating micro and nanoelectromechanical devices (MEMS-NEMS), thought to be the main source of friction at low temperatures, is presented. Quality factors as well as frequency shifts of flexural and torsional modes in doubly-clamped beams and cantilevers are given, showing the scaling with dimensions, temperature and other relevant parameters of these systems. Full agreement with experimental observations is not obtained, leading to a discussion of limitations and possible modifications of the scheme to reach quantitative fitting to experiments. For NEMS covered with metallic electrodes the friction due to electrostatic interaction between the flowing electrons and static charges in the device and substrate is also studied.

Different damping mechanisms in graphene nanoresonators are studied: charges in the substrate, ohmic losses in the substrate and the graphene sheet, breaking and healing of surface bonds (Velcro effect), two level systems, attachment losses, and thermoelastic losses. We find that, for realistic structures and contrary to semiconductor resonators, dissipation is dominated by ohmic losses in the graphene layer and metallic gate. An extension of this study to carbon nanotube-based resonators is presented.Comment: Published version with updated reference

Abstract. -We analyze the dissipation of the vibrations of nano-mechanical devices. We show that the coupling between flexural modes and two-level systems leads to sub-ohmic dissipation. The inverse quality factor of the flexural modes of low frequencies depends on temperature as, providing a quantitative description of the experimental data.Introduction. -Nano-electro-mechanical devices [1, 2] (NEMS) are systems with great potential for applied physics and engineering because of their extreme sensitivity, as probes, to their environment [3][4][5][6][7][8][9]. Furthermore, because of their small size and large surface to volume ratio, these systems are in the crossover region between classical and quantum behavior, and hence of great theoretical interest. Thus, the study of the sources of noise and dissipation in these systems has attracted a great deal of attention [10][11][12][13][14][15][16][17][18]. One of the common realizations of nano-mechanical resonators is a rigid beam of nanoscopic dimensions which vibrates at GHz frequencies [19,20]. The damping of these oscillations has been a subject of intense investigation [10,13,15,16], as it sets a limit to their possible applications.

Abstract. We show that the dynamics of the surface plasmon in metallic nanoparticles damped by its interaction with particle-hole excitations can be modelled by a single degree of freedom coupled to an environment. In this approach, the fast decrease of the dipole matrix elements that couple the plasmon to particle-hole pairs with the energy of the excitation allows a separation of the Hilbert space into low-and high-energy subspaces at a characteristic energy that we estimate. A picture of the spectrum consisting of a collective excitation built from low-energy excitations which interacts with high-energy particle-hole states can be formalised. The high-energy excitations yield an approximate description of a dissipative environment (or "bath") within a finite confined system. Estimates for the relevant timescales establish the Markovian character of the bath dynamics with respect to the surface plasmon evolution for nanoparticles with a radius larger than about 1 nm.PACS. 73.20.Mf Collective excitations -78.67.n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures -71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons