Ar desorption from OsRu coated cathodes (L6)

OsRu and other alloys are used as a top-layer on impregnated W thermionic cathodes to obtain a high emission performance. We apply a cathode with a sputtered OsRu layer in cathode ray tubes (crt). Due to the sputtering process Ar is incorporated in this layer. Part of this Ar desorbs into the crt on first heating. The Ar desorption mechanism has been studied by thermal desorption spectrometry and the metal layer structure has been studied with a variable energy positron beam. It has been found that no Ar bubbles are formed during deposition. Ar is partially released on heating by thermal-vacancy assisted diffusion at ca. 1300 K from the W pellet, and at ca. 1100 K from the OsRu layer. At the same time Ar bubbles are formed in the OsRu layer that desorb at ca. 1800 K.