Abstract

Osmium-ruthenium films with different microstructures were deposited onto dispenser cathodes and subjected to 1000 h of close-spaced diode testing. Tailored microstructures were achieved by applying substrate biasing during deposition, and these were evaluated with scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy before and after close-spaced diode testing. Knee temperatures determined from the close-spaced diode test data were used to evaluate cathode performance. Cathodes with a large {10-11} Os-Ru film texture possessed comparatively low knee temperatures. Furthermore, a low knee temperature correlated with a low effective work function as calculated from the close-spaced diode data. It is proposed that the formation of strong {10-11} texture is responsible for the superior performance of the cathode with a multilayered Os-Ru coating.

Document Type

Article

Publication Date

7-2014

Notes/Citation Information

Published in Journal of Vacuum Science & Technology A, v. 32, no. 4, article 040601, p. 1-6.

Copyright 2014 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in Journal of Vacuum Science & Technology A, v. 32, no. 4, article 040601, p. 1-6 and may be found at http://dx.doi.org/10.1116/1.4876337

Digital Object Identifier (DOI)

http://dx.doi.org/10.1116/1.4876337

Funding Information

This material is based upon work supported by the National Science Foundation under Grant No. CMMI-0928845. Early results of this project were supported by a grant from the Kentucky Science and Engineering Foundation as per Grant Agreement KSEF-148-502-07-223 with the Kentucky Science and Technology Corporation. The authors would like to thank Semicon Associates for their helpful discussions and for supplying cathodes for testing. The authors would also like to acknowledge B. Vancil and eBeam, Inc., for the close-spaced diode tests.

Additional Files
1.tif (5703 kB)
FIG. 1 HIGH-RES. SEM images showing grain growth of 10 W–150 nm [(a) and (b)] and Semicon [(c) and (d)] Os-Ru films after 1000 h in a CSD test. Images (a) and (c) show the films in their as-deposited states, while (b) and (d) show the films after 1000 h at elevated temperature. These images are representative of the grain growth seen in all samples after CSD testing.
Figure 1.pptx (366 kB)
FIG. 1 POWERPOINT. SEM images showing grain growth of 10 W–150 nm [(a) and (b)] and Semicon [(c) and (d)] Os-Ru films after 1000 h in a CSD test. Images (a) and (c) show the films in their as-deposited states, while (b) and (d) show the films after 1000 h at elevated temperature. These images are representative of the grain growth seen in all samples after CSD testing.
2.tif (399 kB)
FIG. 2 HIGH-RES. (Color online) Texture components of Os-Ru films: (a) in the as-deposited state and (b) after 1000 h operation in close-spaced diode testing. The majority of the multilayer film texture components transformed into the {10-11} component. Other films retained a mixture of significant secondary components.
Figure 2.pptx (133 kB)
FIG. 2 POWERPOINT. (Color online) Texture components of Os-Ru films: (a) in the as-deposited state and (b) after 1000 h operation in close-spaced diode testing. The majority of the multilayer film texture components transformed into the {10-11} component. Other films retained a mixture of significant secondary components.
3.tif (382 kB)
FIG. 3 HIGH-RES. (Color online) X-ray diffraction scans of the multilayer coated cathode before (top) and after (bottom) 1000 h of CSD testing. The tungsten substrate and Os-Ru peaks are indicated in the figure. The smaller peaks that appear in the bottom scan correspond to higher-index Os-Ru planes.
Figure 3.pptx (82 kB)
FIG. 3 POWERPOINT. (Color online) X-ray diffraction scans of the multilayer coated cathode before (top) and after (bottom) 1000 h of CSD testing. The tungsten substrate and Os-Ru peaks are indicated in the figure. The smaller peaks that appear in the bottom scan correspond to higher-index Os-Ru planes.
4.tif (585 kB)
FIG. 4 HIGH-RES. (Color online) Current vs temperature plots for the (a) multilayer, (b) 5 W–550 nm, (c) Semicon, and (d) 10 W–150 nm cathodes after 0, 500, and 1000 h of aging. The knee temperature T knee (indicated by an arrow) for each cathode was extracted from these plots by fitting lines to the linear portions of the temperature limited and space charge limited regions and taking their intersection point as <em>T</em> <sub>knee</sub>. The accelerating voltage was 235 V, 230 V, 190 V, and 170 V for the multilayer film, Semicon film, 5 W–550 nm film, and 10 W–150 nm, respectively, after 1000 h.
Figure 4.pptx (117 kB)
FIG. 4 POWERPOINT. (Color online) Current vs temperature plots for the (a) multilayer, (b) 5 W–550 nm, (c) Semicon, and (d) 10 W–150 nm cathodes after 0, 500, and 1000 h of aging. The knee temperature T knee (indicated by an arrow) for each cathode was extracted from these plots by fitting lines to the linear portions of the temperature limited and space charge limited regions and taking their intersection point as <em>T</em> <sub>knee</sub>. The accelerating voltage was 235 V, 230 V, 190 V, and 170 V for the multilayer film, Semicon film, 5 W–550 nm film, and 10 W–150 nm, respectively, after 1000 h.
Table I.GIF (16 kB)
TABLE I. Deposition parameters and texture components of Os-Ru films.
Table II.GIF (17 kB)
TABLE II. Cathode knee temperatures over 1000 h and associated texture components.
Table III.GIF (18 kB)
TABLE III. Comparison of knee temperature, calculated work function, and associated parameters for CSD test cathodes.
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