Journal of Electron Microscopy 47(5): 371-378 (1998)
© 1998 Oxford University Press
Characterization of a refractory surface at a high temperature applied to the Zr-O/W(100) system. On self-recovery function
Department of Applied Physics, Osaka University Suita, Osaka 565, Japan E-mail: shimizu{at}ap.eng.osaka-u.ac.jp
Surface characterization of th Zr-O/W(100) system, widely used as a high stability and high brightness cathode, was performed under operating conditions of ({small tilde}1710 K and {small tilde}10–6 Pa) to better understand its electron emission characteristics. The combined surface analysis techniques employed were Auger electron spectroscopy, ion scattering spectroscopy, high energy electron diffraction, and work function measurement. This study has clarified the nature of the self-recovery function of the Zr-O/W(100) system as follows: excess Zr-O complex on the surface diffuses into the W-substrate during the initial procedure of oxygen processing. These Zr-O complexes are then available to segregate to the surface to compensate for the deficiency of Zr atoms, caused by ion bombardment from residual gases at {small tilde}10–6 Pa during operation. This leads to the very high stability of the electron emissivity. A model of the self-recovery function for oxygen adsorption is also proposed as an oxygen adsorption-deoxidization cycle appearing in Zr-O/W(100) under the operating conditions.
Keywords Zr-O/W(100) TF emitter, self-recovery function, surface characterization
Received 2 April 1988, accepted 15 July 1998