Soft X‑ray High‑Resolution and Time‑Resolved Photoemission: Surface Chemistry and Charge Dynamics in Photoactive Materials
Mathieu G. SILLY
TEMPO Beamline, Synchrotron SOLEIL, France
Photoactive materials — from transition‑metal oxides to semiconductors and hybrid heterostructures — exhibit complex surface and interface phenomena that critically govern their optical, catalytic, and electronic performance. Understanding the interplay between surface chemistry, defects, and charge dynamics, over timescales ranging from a few tens of picoseconds up to one second, is essential for elucidating their photoactivity.
High‑resolution photoemission spectroscopy (HRPES) provides chemical selectivity and surface sensitivity, enabling the identification of oxidation states, defects, and interfacial electronic structures. When combined with time‑resolved photoemission spectroscopy (TRPES), this approach allows direct observation of fast picosecond‑scale dynamics — such as charge transfer and optically induced electronic relaxation — as well as slower nanosecond‑to‑second processes, including trap‑mediated recombination, surface photovoltage relaxations, or charge drift on mesoscopic scales.
These multi‑timescale capabilities are particularly relevant for systems such as hematite under environmental conditions, passivated silicon surfaces, or colloidal nanoparticles coupled to oxides, where simultaneous insight into local chemistry and transient charge dynamics is crucial.
The TEMPO beamline at the SOLEIL synchrotron, dedicated to high‑resolution core‑level photoemission and pump–probe experiments over the ps–s temporal range, provides a unique platform for probing light–matter interactions with both chemical and temporal sensitivity. The combination of HRPES and TRPES thus offers a powerful framework to unravel the mechanisms governing photoactivity and to guide the design of more efficient and durable photoactive materials.
Contact : Mireille Richard-Plouet (PCM)
