Dresden 2026 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 1: Optical Properties I
HL 1.1: Vortrag
Montag, 9. März 2026, 09:30–09:45, POT/0006
Critical-Point Analysis of Ta3N5 Light Absorbers from Room-Temperature Photo-Modulated Spectroscopy — •Matthias Quintern1,2, Johannes Dittloff1,2, Lukas Wolz1, Gabriel Grötzner1,2, Johanna Eichhorn1, and Ian D. Sharp1,2 — 1Technical University of Munich, TUM School of Natural Sciences, Department of Physics, 85748 Garching, Germany — 2Technical University of Munich, Walter Schottky Institute, 85748 Garching, Germany
Tantalum nitride (Ta3N5) thin films are promising photoanode materials for solar water splitting. However, the fundamental nature of the Ta3N5 bandgap remains under debate. To overcome the limitations of conventional Tauc-plot analysis, we built a new combined photoreflectance (PR) and phototransmittance (PT) setup. Our measurements indicate a direct fundamental bandgap of 2.1 eV, but also reveal higher-energy critical points. Furthermore, we find that the PR and PT spectra closely match temperature-corrected transient absorption spectra. The overall differences in the transmission spectra are minor, suggesting that the samples share a similar bulk electronic structure. At the same time, the more surface-sensitive PR signals exhibit greater variations and even additional sub-gap features in some samples. By performing measurements using different pump wavelengths and power densities, as well as employing a phase analysis, we assign individual features of PR spectra to a surface layer. This has implications for out-of-plane charge transport properties and interfacial energies, both of which are crucial parameters for photoelectrochemical performance.
Keywords: Photoreflectance; Spectroscopy; Band structure; Tantalum Nitride; Photoelectrochemistry