Positronium Formation in Nanostructured Metals

Abstract

Positronium formation in Au films was studied using a magnetically guided continuous slow positron beam with variable energy. Black Au film with porous morphology was compared with conventional smooth Au film. In the smooth Au film positronium is formed on the film surface only. The black Au film exhibits porous sub-surface region containing micro-cavities interconnected with surface. Positronium is formed on inner surfaces of microcavities in the sub-surface region and travels through interconnected cavities towards the surface. 3−γ annihilation of ortho-positronium leaves a clear signature in two-dimensional coincidence Doppler broadening spectra. Measures of 3 − γ annihilation contribution calculated from single γ-ray and coincidence Doppler broadening spectra were calculated and compared.

Microstructure and Nanoscopic Porosity in Black Pd Films

“…BM films of various elements are deposited usually by thermal evaporation in carefully adjusted low pressure (∼ 100 Pa) of N 2 gas [7,8]. It has been reported that BMs can be prepared also by magnetron sputtering in Ar with small amount of N 2 [6][7][8][9][10]. In the growth of metallic films in PVD systems contamination from residual atmosphere should be considered [11].…”