9. Improvement of electron gun brightness in conventional scanning electron microscope (SEM) by coating its tungsten filament with a zirconium carbide (ZrC) thin film

• Published in: Vacuum 1978, Vol.28 (12), p.547-550
• Main Authors: Oron, Moshé, Goldstein, Michael
• Format: Article
• Language: English
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/0042-207X(78)90010-6

The purpose of this study was to develop a system which would, by a relatively simple and inexpensive process, increase the brightness of conventional SEM electron-beam guns. The basic idea was to coat the tungsten hairpin filament with a suitable material which would have lower work-function, higher working temperature, lower rate of evaporation and higher resistance to oxidation. Zirconium carbide (ZrC) was chosen as the most appropriate coating material and a systematic series of experiments was conducted with several deposition techniques in order to develop a practical coating process. Chemical vapour deposition (CVD) and vacuum deposition of Zr followed by carburization proved to be the most satisfactory coating processes. Brightness measurements were performed in a commercial scanning electron microscope and compared with values of the original tungsten and LaB 6 guns. The brightness of the coated filaments was found to be 3.5 times higher than that of the conventional tungsten gun and only 5 times lower than the brightness of the expensive LaB 6 gun.