| Numéro |
J. Phys. Colloques
Volume 47, Numéro C2, Mars 1986
32 nd International Field Emission Symposium / 32ème Symposium International d'Emission de Champ
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| Page(s) | C2-59 - C2-66 | |
| DOI | https://doi.org/10.1051/jphyscol:1986209 | |
J. Phys. Colloques 47 (1986) C2-59-C2-66
DOI: 10.1051/jphyscol:1986209
CATHODE BOMBARDMENT STIMULATED MICROSTRUCTURE GROWTH - AVERAGE ION ENERGY
P.R. SCHWOEBEL1, 2 et G.R. HANSON1, 21 The School of Applied and Engineering Physics
2 The National Research and Resource Facility for Submicron Structures, Knight Laboratory, Cornell University, Ithaca, NY 14853, U.S.A.
Abstract
Surface microprotrusions have been associated with cathode initiated vacuum breakdown processes and some interpretations of their formation include surface migration and field enhanced growth. Microstructure growth on field emitters has been observed in association with low temperature (5.0K) adsorption of hydrogen or helium and electron emission currents of 200 to 1000 nA. The presence of adsorbed films (multilayer films for hydrogen) at 5.0K and the general surface damage without stimulated growth at liquid nitrogen temperature suggest that a high dose of low energy ions formed near the emitter surface may activate the surface diffusion. The nucleation of the growth site may result from a number of different events : i) Surface density fluctuations which achieve a critical local field enhancement, ii) Surface damage resulting from the impact of a high energy ion, iii) Threshold surface etching by ion sputtering. A model calculation of the ion energy indicates that at 5.0K, ≈ 86% of the hydrogen ions have a kinetic energy less than 100 ev (0.35 V/Å Applied Field, 3300 V). Similar effects are demonstrated for He+ cathode bombardment. Low energy helium ion bombardment activated surface self diffusion in the presence of an applied field provides several technical advantages for high brightness field ion source development.