AVS 56th International Symposium & Exhibition
    Thin Film Wednesday Sessions
       Session TF-WeM

Paper TF-WeM6
Preparation and Microstructure of Silver Nanoparticles Embedded into a Flourocarbon Matrix Prepared by RF and DC Sputtering

Wednesday, November 11, 2009, 9:40 am, Room B4

Session: Nanostructuring Thin Films I
Presenter: A.F. Talledo Coronado, Universidad Nacional de Ingenieria, Peru
Authors: D.G. Vásquez Mazzoti, Universidad Nacional de Ingenieria, Peru
A.F. Talledo Coronado, Universidad Nacional de Ingenieria, Peru
C. Benndorf, University of Hamburg, Germany
Correspondent: Click to Email
Composite materials consisting of metal nanoparticles embedded in transparent dielectric materials are interesting materials due the size effects induced by the nanoparticles. We report about the preparation of fluorocarbon thin films with embedded silver nanoparticles and their characterization with UV-VIS spectroscopy, XPS (X-ray induced photoelectron spectroscopy), IR (infrared spectroscopy) and HRTEM (high resolution transmission electron microscopy). Further, the surface free energy was determined from contact angle measurements using different liquids. The metal-dielectric nanocomposites with a layered structure were prepared by switching alternatively the substrates (glass or stainless steel) from an RF powered Teflon target towards an Ag target powered by DC. The high resolution XPS spectra from the C 1s region displayed four peaks (on stainless steal substrates) with positions of 284.5, 286.5, 288.6 and 290.7 eV, related to C-Hx, C-F, C-F2 and C-F3 bonds, respectively. For comparison, we measured the XPS spectrum from a Teflon surface (after scratching the surface). From this surface, the carbon 1 s region was dominated by two peaks, located at 284.6 (C-Hx) and 289.0 eV (C-F2). The different composition of the sputtered films is due to the plasma process, which produces fragments like F, CF, CF2 and CF3 radicals and ions. The incorporated Ag nanoparticles gave only weak XPS signals from the Ag 3d doublet around 368 - 374 eV. UV-VIS spectra, measured in the range of 300 - 800 nm in transmission, showed with the presence of the Ag nanoparticles pronounced absorption peaks at around 420 to 480 nm, depending on the amount of incorporated Ag and different preparation conditions. This absorption maximum is related by us, in accordance with other authors, to the surface plasmon loss of the Ag nanoparticles where the loss energy depends on the particle size and form, the concentration of the particles and the nature (dielectric constant) of the surrounding matrix. HRTEM pictures showed the presence of Ag nanoparticles with sizes between 5 and 50 nm. The filling factor of Ag (within the fluorocarbon matrix) was about 0.3. Crystalline planes from the Ag nanoparticles could be observed with (200) and (111) orientation. The evaluation of the lattice spacing resulted in d200 = 0.204 and d111 =0. 237 nm which is within 1% of the bulk Ag values. The surface free energy of our films was determined by the observation of the contact angle of liquid drops, using water, ethyl alcohol and olive oil. The evaluation was done following the method of Zisman. We obtained a value around 15mN/m, which is approximately 50% of the value reported for bulk Teflon.