Resharpened tips show high optical field enhancement – published in Nanoletters

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There has been research and development on novel electron sources for many decades, for example on sharp metal tips as a source in electron microscopes. These tips are usually electrochemically fabricated and have a minimum tip radius of about 10 nm. For photoemission experiments that exploit the extreme near-field optical gain of an incident laser pulse at the sharp needle tip, it is of particular interest to optimize these tips with respect to tip radius and aperture angle. Together with colleagues from the Department of Materials Science and Engineering at FAU, we have now been able to show that electrochemically produced metal tips can be subsequently sharpened with neon ion bombardment in an ultrahigh vacuum, resulting in tips with a radius of only 1 nm. Using strong-field physics, in particular the interpretation of backscattering spectra of electrons, we now show in our new publication at Nanoletters that such tips exhibit much higher near-field optical enhancement and can be used as a laser-driven pulsed electron source. The publication is here.