Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 23: Ultra-fast phenomena
HL 23.6: Talk
Tuesday, March 17, 2020, 11:15–11:30, POT 112
Femtosecond laser-induced electron emission from nanodiamond-coated tungsten needle tips — •Alexander Tafel, Stefan Meier, Jürgen Ristein, and Peter Hommelhoff — Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen
We present femtosecond electron emission from a tip-shaped metal-semiconductor heterostructure. By coating tungsten needle tips with thin nanodiamond (50-200 nm), we combine the high electron beam quality of tip-shaped emitters with the robustness and the negative electron affinity of diamond.
Due to the high peak intensity of femtosecond laser pulses, electrons can be photoexcited for wavelengths from the infrared (1932 nm) to the ultraviolet (235 nm) because multiphoton excitation becomes efficient over the entire spectral range. Depending on the laser wavelength, we find different dominant emission channels identified by the number of photons needed to emit electrons. Based on the band alignment between tungsten and nanodiamond, the relevant emission channels can be identified as specific transitions in diamond and its graphitic boundaries.
Emission is stable at all wavelenths and bunch charges tested (up to 400 electrons per pulse). We infer a normalized emittance of less than 0.20 nm rad and a normalized peak brightness higher than 1.2 · 1012 A m−2 sr−1.
Reference: A. Tafel et al., Phys. Rev. Lett. 123, 146902, 2019.