Microstructure and Nanoscopic Porosity in Black Pd Films |
| O. Melikhovaa, J. Čížeka, P. Hruškaa, b, F. Lukáča, c, M. Novotnýb, J. More-Chevalierb, P. Fitld, M.O. Liedkee, M. Butterlinge, A. Wagnere
aFaculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Praha 8, Czech Republic bInstitute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czech Republic cInstitute of Plasma Physics of the Czech Academy of Sciences, Za Slovankou 3, 182 00 Praha 8, Czech Republic dDepartment of Physics and Measurements, University of Chemistry and Technology, Technická 5, 166 28 Praha 6, Czech Republic eInstitute of Radiation Physics, Helmholtz Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany |
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| In the present work the microstructure of a black Pd film prepared by thermal evaporation and a glossy Pd film deposited by magnetron sputtering was compared. While the glossy Pd film exhibits typical polycrystalline structure with column-like grains, the black Pd film has fractal-like porous structure. Positron annihilation spectroscopy revealed that positronium is formed in nanoscopic cavities of the black Pd film. In conventional metals positronium does not form due to screening by conduction electrons. However, in porous metals containing nanoscopic porosity a thermalized positron may pick an electron on inner surface of a pore and escape into a cavity forming positronium. The average size of nanoscopic pores in the black Pd film was determined from the lifetime of long-lived ortho-positronium component. |
DOI:10.12693/APhysPolA.137.222 topics: positron annihilation spectroscopy, positronium, palladium, thin film |