Effects of electron irradiation on structure and bonding of SF6 on Ru(0001)

Анотація

Electron stimulated desorption ion angular distribution (ESDIAD) and temperature programmed desorption (TPD) techniques have been employed to study radiation-induced decomposition of fractional monolayer SF₆ films physisorbed on Ru(0001) at 25 K. Our focus is on the origin of F⁺ and F^- ions, which dominate ESD from fractional monolayers. F^- ions escape only in off-normal directions and originate from undissociated molecules. The origins of F⁺ ions are more complicated. The F⁺ ions from electron stimulated desorption of molecularly adsorbed SF₆ desorb in off-normal directions, in symmetric ESDIAD patterns. Electron beam exposure leads to formation of SF_x (x = 0 - 5) fragments, which become the source of positive ions in normal and off-normal directions. Electron exposure > 10¹⁶ cm^{- 2} results in decomposition of the entire adsorbed SF₆ layer.