Ultrafast exciton formation at the ZnO(10$\overline{\text{1}}$0) surface

Abstract

We study the ultrafast quasiparticle dynamics in and below the ZnO conduction band using femtosecond time-resolved two-photon photoelectron spectroscopy. Above band gap excitation causes hot electron relaxation by electron-phonon scattering down to the Fermi level $E_{\text{F}}$ followed by ultrafast (200 fs) formation of a surface exciton (SX). Transient screening of the Coulomb interaction reduces the SX formation probability at high excitation densities near the Mott limit. Located just below the surface, the SX are stable with regard to hydrogen-induced work function modifications and thus the ideal prerequisite for resonant energy transfer applications.

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• Image potential states of ultrathin NiO films: A time-resolved two-photon photoemission study
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• Probing excitons with time-resolved momentum microscopy
• Nanoscale Transport of Surface Excitons at the Interface between ZnO and a Molecular Monolayer
• Localization-dependent charge separation efficiency at an organic/inorganic hybrid interface
• Excitonic Bloch equations from first principles
• Coherence and de-coherence in the Time-Resolved ARPES of realistic materials: an ab-initio perspective