Microscopic description of the surface dipole plasmon in large Na_N clusters (950 < N < 12050)

Fully microscopic RPA/LDA calculations of the dipole plasmon for very large neutral and charged sodium clusters, Na_N^Z+, in the size range 950 < N < 12050 are presented for the first time. 60 different sizes are considered altogether, which allows for an in-depth investigation of the asymptotic behavior of both the width and the position of the plasmon.Comment: Latex/Revtex, 4 pages with 4 Postscript figures, accepted for publication in Physical Review

Nondestructive dynamic characterization of nanocrystalline diamond membranes for flexural plate wave sensors

Nanocrystalline diamond (NCD) is a promising material for the fabrication of highly sensitive flexural-plate-wave (FPW) sensors. The design of FPW sensors requires the determination of the mechanical properties of a vibrating thin-film membrane. In this paper, a method to investigate the mechanical resonance of NCD membranes is presented. Membranes with lateral dimensions in the millimeter range and 1.2-μm thick were excited in air by a loudspeaker, and the resonance mode shapes were recorded optically with a stroboscopic interferometer. The resonance frequencies helped in determining directly the mechanical parameter of interest for the design of diamond-based FPW devices and the residual stress in the NCD layer. This method allows the rapid investigation of prototype materials without requiring an integrated transduction system and can be applied to analyze structures with the actual dimensions of FPW sensors. The experimental results are used to assess the sensing properties of FPW devices with NCD membranes, which are enhanced with respect to classical materials such as silicon-based materials

Commercial developments of nano-crystalline diamond - Two prototypes as case studies

Novel technologies for synthesis of nano-crystalline diamond (NCD) enable industrial production allowing large area deposition on a variety of substrate materials - at reasonable price. New perspectives for future innovative products emerge demonstrated by two case studies in the field of micro electro-mechanical systems (MEMS) sensors (case a) and medical implant devices (case b). a) This study comes as a preliminary step towards the integration of NCD thin film membranes in gravimetric sensors with low detection limits. We investigate theoretically and experimentally the mass sensing characteristics of composite thin Film Bulk Acoustic Resonator (FBAR) as a function of the side exposed to a mass perturbation. b) The aim of this study was to demonstrate the influence of different surface terminations of NCD on surface potentials and subsequently its influence on in vivo connective tissue healing. NCD-coated implants were evaluated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM)-surface potential measurements. After in vivo integration of the NCD-membranes into the subdermal layer of Wistar rats and subsequent histological evaluation it was demonstrated that the number of cells increased significantly at the O-terminated NCD and the scar tissue formed was less tight. Thus, a promising technique for controlling connective tissue adhesion in vivo is presented. © 2008 Elsevier B.V. All rights reserved

Grazing-incidence small-angle X-ray scattering study on ultra nanocrystalline diamond films

In this work, an ultrananocrystalline diamond film was studied with grazing-incidence small-angle X-ray scattering (GISAXS) to determine the diamond grain size and average distance of the grains with a non-destructive method and with excellent sampling statistics. The measured 2D GISAXS patterns were modelled with the assumption of monodisperse spheres. The best fits were obtained with the "buried layer" model where the spheres are correlated within the film plane. This correlation was approximated with a two-dimensional Percus–Yevick structure factor. The average diamond grain size of D = 8.0–8.5 nm and a centre-to-centre distance of the grains with 10.4–11.9 nm agrees well with transmission electron microscopy results of comparable samples