Simple, efficient technique for exposing surfaces to hydrogen atoms

A device is described for the efficient generation of H atoms by thermal dissociation of H-2. Hydrogen molecules exit a small hole in the wall of a Mo tube (with a solid end cap) and strike a hot W foil held at similar to 45 degrees to the flux. The sample is positioned to intercept the H-atom flux leaving the foil. The technique is demonstrated by exposing a Si (100)-(2x1) surface to the H-atom flux and the efficiency for producing the H-induced (2x1)-->(1x1) conversion compared with that of the conventional approach using a W filament and a random H-2 flux.