Multiphoton electron emission from diamond-coated nanotips: published in Physical Review Letters
Diamond is a highly interesting material for electron sources because it is not only mechanically robust, chemically inert and thermally conductive, but also exhibits negative electron affinity if the surface is saturated with hydrogen. Due to this special property, diamond has a low work function and can have a significantly higher quantum efficiency than materials with positive electron affinity, i.e. almost all other materials. Having reported on the fabrication of nanodiamond-coated tungsten tips, we characterize the photoemission of electrons from the tip by illuminating it with ultrashort laser pulses in our current publication. The high photon density of femtosecond laser pulses render electron emission by multiphoton absorption possible. We measure the number of photons required per emitted electron at different wavelengths and can so identify specific emission channels in the complex band diagram of the present heterostructure. In addition, we characterize the potential application of our nanodiamond-coated tips as ultrafast electron sources. We find that the brightness is already comparable to sources used in today’s electron microscopes, for example, and the stability is even better.