Photocathodes have been proposed as a technology for achieving multiple independently modulated electron beams for advanced electron-beam lithography applications. Thin-film gold photocathodes are of particular interest because they offer the potential of practical multi-beam electron sources that can be easily fabricated using thin-film deposition techniques without special environmental or handling techniques to achieve the desired stability and performance. A series of gold thin films were deposited on sapphire, using a developed baseline process and subsequently studied for photoemission in the 200 to 300 nm range. The study focused on the impact of surface chemistry, thermally driven microstructural changes, and adsorbed gases on photoemission. We have achieved current densities between 1 - 4 amp/cm2 with electron energies spread of less than 0.5 eV (laser illumination wavelength of 257 nm). The maximum current values, stability and minimum emitter spot size are limited primarily by excess temperature rise in the film caused by the laser illumination. In this paper we propose time, temperature and environmental dependent degradation mechanisms of gold thin film photocathodes which verifies their potential for advanced electron-beam lithography applications.
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