6.2: Optimizing osmium-ruthenium films to inhibit tungsten interdiffusion

Osmium-ruthenium thin films were deposited on porous tungsten pellets, at the same time as cathode assemblies, to investigate possibilities for minimizing interdiffusion. Previous studies had identified promising film characteristics for inhibiting tungsten interdiffusion. For example, it was found that a 5W-substrate-biased film of 550 nm thickness exhibited high structural and compositional stability, and several other films exhibited promising properties as well. These films were produced and annealed, then analyzed for composition. Emission tests of M-type cathode assemblies, coated with the same candidate films, were performed to assess the degree of lifetime improvement imparted by the films to the cathodes.