Monochromatic Electron Photoemission from Diamondoid Monolayers

Abstract

We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flatpanel displays.

Diamondoid coating enables disruptive approach for chemical and magnetic imaging with 10 nm spatial resolution

“…To benchmark, we also compare this new data with earlier data acquired at 55 eV 10 (green), as well as data obtained using a UV source 31 (blue line). The electron energy mono-chromatization effect still functions as effectively at 700 eV, which is an order of magnitude higher than earlier experiments using 55 eV photons 10 . In summary, we find similar energy spreads after excitation with 700eV X-ray photons on a diamondoid covered surface as after excitation with 5eV UV photons from a bare surface.…”

“…This property combined with strong electron phonon scattering and extremely short mean free path in diamondoid caused monochromatization of secondary electrons emitted from a metal surface 9 . The electron emission spectrum is characterized by a sharp peak with a bandwidth of 0.3eV (FWHM), which surpasses the value that is obtained on bulk diamond 10,11 . This particular property generated strong interest in the photo-cathode community since it opens the door to a completely new and disruptive approach to design new generations of photo-cathodes with superior emission properties.…”

“…However, this comes at significant costs (>$1M) compared to conventional PEEM (~$100k) and makes the operation much more complex. In this paper we show how the effect of chromatic aberrations in X-PEEM can be minimized without compromising the functionality or the setup of the instrument at minimal cost using a thin diamondoid coating, by a layer of [121]tetramantanethiol 10,11,25 , which form a self-assembled monolayer (SAM) on selected metal surfaces 26,27,28,29,30 . Our findings represent the first successful application of diamondoids to effectively improve the performance of an electron cathode.…”

“…Upon coating the sample surface with a monolayer of diamondoids, the energy distribution of the emitted electrons, however, changes dramatically. The negative electron affinity and efficient electron scattering process cause the electrons passing through the diamondoid surface layer to be scattered and to relax to the lowest unoccupied molecular orbital (4) before they are emitted into the vacuum 10,11 . Consequently their energy distribution is much smaller as shown by the red curve in Figure 1., which has been acquired using X-rays with a photon energy of 700 eV from a diamondoid coated Au surface using a Scienta hemispherical analyzer.…”

Attosecond Transversal Streaking to Probe Electron Dynamics at Surfaces

“…Recent investigations of the photoemission of diamondoid (e. g. tetramantane) coated metals revealed a nearly monochromatic photoelectron spectrum and ultra-short electron transit times. [1,2] Highly excited electrons from the metal are efficiently transferred to the molecule LUMO, from which they are supposed to be instantly emitted due to the negative electron affinity (NEA).…”