REFLECTOR ATOMIC-HYDROGEN SOURCE - A METHOD FOR PRODUCING PURE ATOMIC-HYDROGEN IN ULTRAHIGH-VACUUM

A tungsten filament atomic hydrogen source placed in an effusive H-2 molecular beam has been combined with a cryogenically cooled Pyrex reflector. This arrangement permits efficient production and transfer of atomic hydrogen to a sample surface by a non-line-of-sight route. The arrangement eliminates most radiation heating of the sample. With the beam source, high local H-2 gas densities and atomic hydrogen production rates in the filament region may be achieved without producing excessive gas loads in an ultrahigh vacuum system. A silicon(100) crystal sample was used in this study. The indirect source protects the sample from possible metal contamination evolving from the hot tungsten filament, and efficiently delivers only atomic and molecular hydrogen species to the sample. The efficiency of this arrangement has been quantitatively compared to a line-of-sight filament source of atomic hydrogen.