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HL: Fachverband Halbleiterphysik
HL 24: Functional Semiconductors for Renewable Energy Solutions (joint session HL/KFM)
HL 24.4: Vortrag
Mittwoch, 7. September 2022, 15:45–16:00, H36
Effects of Defects on the Optoelectronic Properties of Ta3N5 Thin Films — Lukas M. Wolz, •Gabriel Grötzner, Laura I. Wagner, Ian D. Sharp, and Johanna Eichhorn — Walter Schottky Institut, Technische Universität München
For photoelectrochemical energy conversion, metal nitride semiconductors have the potential to overcome several limitations associated with the more intensively investigated class of metal oxides. Among these materials, Ta3N5 is especially promising, possessing a bandgap of ∼2.2 eV and effective long-range charge transport. However, the (opto)electronic and photoelectrochemical properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and low-valent Ta cations. To identify the impact of such defects on the material properties, we prepare Ta3N5 via two different synthetic routes. As precursor, TaxNy and TaxOy thin films were deposited by magnetron sputtering and were subsequently annealed at high temperatures in NH3 to form Ta3N5. Both films are homogenous and reveal the formation of phase-pure orthorhombic Ta3N5. Compared to nitride-derived Ta3N5, the oxide-derived films are characterized by higher structural disorder as well as higher oxygen and lower nitrogen concentrations. Despite these higher defect concentrations, the oxide-derived Ta3N5 films exhibit improved stability under photoelectrochemical operation conditions, though both films show similar photoelectrochemical performance. The improved understanding of defect properties and their impact on PEC stability provides a path to tailored optimization of photoelectrode properties.