Ana M. Tarditi

Controlling the work function of a diamond-like carbon surface by fluorination with XeF2

Thin diamond-like carbon films were subjected to fluorination with gaseous XeF2 under ultrahigh vacuum conditions in order to increase the work function of the diamond-like carbon surface. Changes in the work function and surface composition were monitored with UV photoemission spectroscopy and x-ray photoemission spectroscopy, respectively. Successive XeF2 exposures raised the work function by as much as 1.55 eV. Surprisingly, approximately half of the increase in the work function occurred while the coverage of fluorine remained below 0.02 monolayers (ML). This suggests that initial doses of XeF2 remove extrinsic adsorbates from the diamond-like carbon film and that fluorine desorbs with the reaction products. Increasing the exposure of the diamond-like carbon to XeF2 leads to the expected covalent fluorination of the surface, which saturates at fluorine coverages of 6 F atoms/nm2 (∼0.3 ML). Annealing of the diamond-like carbon to temperatures above 850 K was required to reduce the surface fluorine conc...

3.1 Electroless Plating of Pd Binary and Ternary Alloys and Surface Characteristics for Application in Hydrogen Separation

Electroless plating has been defined as a controlled autocatalytic deposition of a continuous layer on a catalytic surface by the reaction of a complex compound and a chemical reducing agent. This method allows the easy preparation of films using simple equipment and any type of support with low thickness. Palladium-based layers are able to separate hydrogen selectively because of the high solubility and diffusivity of hydrogen atoms in their lattice. The electroless deposition and characterization of Pd-based binary and ternary alloys are discussed taking into account their superior properties concerning hydrogen permeability and/or chemical resistance.