Effective work functions for thermal positive-ionic and electronic emissions from tantalum heated in a high vacuum

✍ Scribed by Hiroyuki Kawano; Seiji Matsui; Hajime Kobayashi; Yongfa Zhu

• Book ID: 104265897
• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 278 KB
• Volume: 48
• Category: Article
• ISSN: 0042-207X
• DOI: 10.1016/s0042-207x(97)00050-x

✦ Synopsis

To elucidate the thermionic property of a polycrystal surface of Ta heated in an easily attainable high vacuum (-1O-5 Pa), the effective work functions (4' and 4") for thermal positive-ionic and electronic emissions from the surface were measured as a function of surface temperature (T). ( 1) Above -18OOK, 4' and 4" were constant at -5. I and 4.3 eV, respectively, corresponding to a clean surface of Ta. ( 2) As T decreased from -1800 to 15OOK, 4' and rj" were increased up to -5.3 and 4.4 eV, respectively, mainly by adsorption of residual gases. ( 3) Below -1500 K, 4' showed different patterns according to the sample species (RbCI, RbBr, CsF or CsCl), ranging from -4.9 up to 6.7eV. This was caused by co-adsorption of each sample and the gases. ( 4) The thermionic contrast (6 -4") was constant at -0.90f O.O3eV, showing not to depend on T.