Preparation and properties of sputtered MgO/Au, MgO/Ag, and MgO/Ni cermet films

Finely grained films of three cermets-MgO/Au, MgO/Ag, and MgO/Ni-have been grown by rf sputtering from composite targets. Electron-microscopic studies show that MgO/Au and MgO/Ag films consist of small crystallites (usually <150 Å) of both MgO and Au or Ag. In MgO/Ni films, it appears that amorphous Ni particles are embedded in a polycrystalline MgO matrix. These cermet films are good secondary-electron emitters, especially in cases where differential-sputtering effects are large. In MgO/Au films, the Au particles sputter much faster than MgO resulting in a MgO-rich surface layer. In MgO/Ag films, the differential-sputtering effect is smaller, probably due to stronger interaction between MgO and Ag crystallites. In MgO/Ni, the Ni particles sputter slower than MgO resulting in a slightly Ni-rich surface (and hence in poorer electron-emission properties). The small particle sizes and the presence of metallic particles in the bulk of the films greatly reduce surface charging.