Demonstration of Li-based alloy coatings as low-voltage stable electron-emission surfaces for field-emission devices

Alkali metals have extremely low work functions and are, therefore, expected to result in significant enhancement of the electron emission if they are used as coatings on Mo or Si microtip field-emission arrays (FEAs). However, the alkali metals are physically and chemically unstable in layers exceeding a few Å in thickness. Maximum enhancement of electron emission occurs for alkali-metal layers 0.5-1 ML thick, but it is extremely difficult to fabricate and maintain such a thin alkali-metal coating. We present here an alternative means of producing chemically and thermally stable, self-replenishing lithium coatings approximately 1 ML thick, which results in a 13-fold reduction in the threshold voltage for electron emission compared with uncoated Si FEAs.