Photoemission spectroscopy using virtual photons emitted by positron sticking: a new probe of the top layer surface electronic structure

Abstract

We present a spectroscopic method which utilizes virtual photons to selectively measure the electronic structure of the top-most atomic layer. These virtual photons are created when incident positrons transition from vacuum states to bound surface states on the sample surface and can transfer sufficient energy to excite electrons into the vacuum. The short interaction range of the virtual photons restricts the penetration depth to approximately the Thomas-Fermi screening length. Measurements and analysis of the kinetic energies of the emitted electrons made on a single-layer of graphene deposited on Cu and on the clean Cu substrate shows that the ejected electrons originate exclusively from the top-most atomic layer. Moreover, we find that the kinetic energies of the emitted electrons reflect the density of states at the surface. These results demonstrate that this technique will be a complementary tool to existing spectroscopic techniques in determining the electronic structure of 2D materials and fragile systems due to the absence of subsurface contributions and probe-induced surface damage.

References in corpus (8)

• All-graphene integrated circuits via strain engineering
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• Experimental determination of the state-dependent enhancement of the electron-positron momentum density in solids
• Direct observation of electron emission as a result of a VVV Auger transition in the valence band of Graphene
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• The healing mechanism for excited molecules near metallic surfaces
• Positronium formation in graphene and graphite

Cited by in corpus (2)

• Quantum Monte Carlo study of Doppler broadening of positron annihilation radiation in semiconductors and insulators
• Monte Carlo analysis of the contributions of long-lived positronium to the spectra of positron-impact-induced secondary electrons measured using an annihilation-gamma-triggered time-of-flight spectrometer