Effects of substrate bias on microstructure of osmium-ruthenium coatings for porous tungsten dispenser cathodes

Wen Chung Li, Scott Roberts, T. John Balk

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Osmium-ruthenium (Os-Ru) films used as coatings for porous tungsten (W) dispenser cathodes were investigated in this study. By applying different levels of substrate biasing power during sputtering, the texture of deposited Os-Ru films varied between {0002}, {10-10}, and {10-11} in this hexagonal close-packed alloy. Furthermore, film texture changed from one preferred orientation to other preferred orientation(s) during annealing (at 1050 °CB for 10 min), during which the microstructure of certain Os-Ru films changed from a columnar to an equiaxed grain morphology. Due to a low degree of texture transition during annealing and due to the high compositional and structural stability of the Os-Ru grains, a 5 W bias power appears to be best for film deposition. In addition, the 5 W biased Os-Ru films transformed completely into a basal plane texture, which has the highest planar density, and grain size increased significantly (from ∼20 to ∼100 nm) during annealing, all while maintaining a columnar grain structure. These characteristics are believed to be helpful in inhibiting interdiffusion between the W substrate and the Os-Ru film. Preventing or slowing the interdiffusion of W atoms can improve the lifetime and even the performance of dispenser cathodes.

Original languageEnglish
Pages (from-to)805-811
Number of pages7
JournalIEEE Transactions on Electron Devices
Issue number5
StatePublished - 2009

Bibliographical note

Funding Information:
Manuscript received October 1, 2008; revised December 1, 2008. Current version published April 22, 2009. This work was supported in part by the Kentucky Science and Engineering Foundation under Grant Agreement KSEF-148-502-07-223 with the Kentucky Science and Technology Corporation. The review of this paper was arranged by Editor W. Menninger.


  • Cathode
  • Coating
  • Osmium (Os)
  • Ruthenium (Ru)
  • Tungsten (W)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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