Berlin 2024 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 38: Oxide Semiconductors II
HL 38.1: Talk
Thursday, March 21, 2024, 09:30–09:45, ER 325
Energy and thickness dependent intensity characteristics of simultaneous XEOL-XAS measurements of ZnO — Sergiu Levcenko1, Konrad Ritter1, Hans H. Falk1, Timo Pfeiffelmann1, Lukas Trefflich1, Edmund Welter2, Marius Grundmann1, and •Claudia S. Schnohr1 — 1Felix Bloch Institute for Solid State Physics, Leipzig University, Germany — 2Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
X-ray excited optical luminescence (XEOL) is used to study optically active centers in a variety of materials. Combined with spatial and temporal resolution, XEOL is applied for multimodal analysis of hetero- and nanostructures while simultaneous XEOL and X-ray absorption spectroscopy (XAS) experiments can provide element and site selective structural information. However, no comprehensive model for the X-ray fluorescence (XRF) and XEOL intensities has yet been established. Therefore, we performed a systemtatic XEOL-XAS study of ZnO with 1 to 500 µm thicknesses at beamline P65 of PETRA III. The XRF and XEOL near-band-edge (NBE) intensities show a positive edge jump when scanning across the Zn K-edge for all samples. In contrast, the XEOL defect signal exhibits a positive edge jump for thin samples but an inverted intensity profile for thick samples. We demonstrate that all energy and thickness dependent intensity features for XRF, XEOL NBE and XEOL defect signals can be reproduced by a generalized model if the (i) experimental geometry, (ii) creation of excitations, (iii) diffusion and recombination of generated carriers and (iv) re-absorption of XRF and XEOL photons are taken into account.
Keywords: Zinc oxide; X-ray excited optical luminescence; X-ray fluorescence; X-ray absorption spectroscopy