Electronic Excitations at Surfaces and Interfaces

Absorption of light by matter goes along with the excitation of charge carriers. The decay of these excitations critically determines the rate at which light energy is finally transferred to the rest of the solid. Understanding carrier relaxation is, therefore, of major relevance for processes such as light harvesting in solar cells, photochemical reactions at surfaces or laser assisted machining of solids. More...

Image for ElectronicExcitationsCarrier dynamics in graphite probed at the H-point [3];

We use time-resolved two-photon photoemission (TR-2PPE) and time- and angle-resolved photoelectron spectroscopy (TR-ARPES) to study the dynamics of carrier relaxation in solids and at surfaces. Examples of our work includes the study of charge-transfer processes in model-type adsorbate-surface systems [1], hot electron relaxation processes in metals [2] and the carrier thermalization in graphite-based materials [3].

Results of a time- and angle-resolved photoemission study (TR-ARPES) of graphite. The right-hand graph results from an integration of the experimental data along the electron momentum k// . It illustrates the heat up and cool down of the electron system after absortion of an ultrashort laser pulse.

[1] “Excited states in the alkali/noble metal surface systems: a model system for the study of charge transfer dynamics at surfaces“ J.P. Gauyaqc., A.G. Borisov, M. Bauer, Prog. Surf. Sci. 82, 244 (2007).  doi:10.1016/j.progsurf.2007.03.006

[2] “Hot electron lifetimes in metals probed by time-resolved two-photon photoemission" M. Bauer, A. Marienfeld, and M. Aeschlimann; Prog. Surf. Sci. 90, 319 (2015). doi:10.1016/j.progsurf.2015.05.001

[3] "Hot Electron Cooling in Graphite: Supercollision versus Hot Phonon Decay" A. Stange, C. Sohrt, L.X. Yang, G. Rohde, K. Janssen, P. Hein, L.-P. Oloff, K. Hanff, K. Rossnagel, and M. Bauer; Phys. Rev. B 92, 184303 (2015), doi:10.1103/PhysRevB.92.184303