Field-induced redistribution processes in adsorption layers of hydrogen on ruthenium

The field-induced effects in hydrogen layers on ruthenium field emitters, which had been observed before, have been investigated in more detail in two laboratories. Raising the field causes an unusual increase of emission, due to a decrease of work function, on certain planes and vicinals (mostly on and around the {110}) of the Ru field emitter. The extent, rate of appearance, and disappearance, of this effect depend on field, coverage and temperature. It is shown that the cause is mainly the removal of hydrogen from these areas. However, all earlier reports on similar effects in other systems have shown the opposite sign of the dependence on the direction of the electric field. The discussion of possible mechanisms shows that no fully satisfactory explanation can be given at present.