Erosion of frozen SF 6 by electron bombardment

Abstract

Mass spectra were taken of neutral particle fluxes sputtered from frozen SF 6 gas during bombardment by electrons with an energy of 750 eV. This spectrum is very different from that of gaseous SF 6. In particular the small SF x fragments are much more abundant in the sputtering case. Also time of flight spectra have been taken. These show different TOF distributions for different particles. Conversion to energy spectra show these also to be different for the various sputtered species. F 2 molecules have energies up to a few tenths of an eV, the other particles up to a few eV. From these observations we infer that 1) the conversion of electronic into kinetic energy is caused mainly by dissociative excitation and/or ionization, 2) the various species are sputtered as such, 3) F 2 molecules are obtained from recombination of F atoms and subsequent desorption from the surface, 4) the results cannot be explained by assuming degradation of the initial electronic energy into a thermal spike.