Scanning electron and tunneling microscopy of palladium–barium emitters

Autor: U.P Volkov, S.V Semenov, V.B Baiburin, Artem S. Semenov
Rok vydání: 2003
Předmět:
Zdroj: Applied Surface Science. 215:269-272
ISSN: 0169-4332
DOI: 10.1016/s0169-4332(03)00291-5
Popis: The results of study of metal-alloyed palladium–barium emitters’ of modern very high frequency high-powered electronic vacuum tubes by scanning electron microscopy (SEM) and scanning tunneling microscopy/spectroscopy (STM/STS) are presented. Since the Pd/Ba foil surface is fairly smooth and is not oxidized in air STM/STS investigations are carried out in air in normal laboratory environment. SEM and STM images show that the emitter surface has a complex porous structure. The cathode surface study by STS in tunneling gap modulation mode allowed to take a map of phase distribution with various work function values and high lateral resolution. Obtained images demonstrate the presence of three phases on the Pd/Ba emitter surface, viz. barium–oxygen compounds, intermetallic, and palladium. As it is seen from presented STS image the phase with a low work function value (barium oxides) is concentrated along boundaries of the substance inclusions with work function corresponding to the intemetallic compound Pd 5 Ba. This supports the model of low work function areas obtained via Ba segregation from the intermetallic compound and oxidation. The presented methods may be used in the Pd/Ba cathode manufacturing process for increasing the yield of electronic devices in microwave tube production and optimize the emitters’ characteristics.
Databáze: OpenAIRE
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