title: Evidence for photogenerated intermediate hole polarons in ZnO.
abstract: Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection-absorption spectroscopy (IRRAS) with a time resolution of 100 ms. For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength.
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Hikmet
authors.initials: H
authors.lastname: Sezen
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Honghui
authors.initials: H
authors.lastname: Shang
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Bebensee
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Chengwu
authors.initials: C
authors.lastname: Yang
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Buchholz
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Alexei
authors.initials: A
authors.lastname: Nefedov
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Heissler
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Carbogno
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Scheffler
authors.affiliation: 1] Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany [2] COMP/Department of Applied Physics, Aalto University School of Science, P.O. Box 11100, FI-00076 Aalto, Finland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Rinke
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute of Functional Interfaces (IFG), 76021 Karlsruhe, Germany.
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll