Dresden 2020 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 24: Functional semiconductors for renewable energy solutions I (joint session HL/CPP)

HL 24.4: Talk

Tuesday, March 17, 2020, 11:00–11:15, POT 151

Reactive sputtering of tantalum nitride for photoelectrochemical energy conversion — •Laura Wagner, Chang-Ming Jiang, and Ian Sharp — Walter Schottky Institut, Technische Universität München

Nitride semiconductors have gained increasing attention for photoelectrochemical (PEC) energy conversion. Traditionally, oxides have been widely investigated as photoelectrodes due to their chemical stability and versatile synthesis pathways; however oxide materials that simultaneously fulfill the efficiency and stability requirements have yet to be found. Many nitrides compounds are theoretically predicted to be semiconducting, though only a small fraction of these materials have been synthesized. Given their higher covalency compared to oxides, these nitrides may be promising candidates for PEC applications. Among transition metal nitrides, Ta3N5 has 2.1 eV bandgap and suitable valence band position for driving the water oxidation. While most studies perform nitridation on Ta or TaOx in order to obtain Ta3N5 thin films, we prepare Ta3N5 on various substrates by reactive magnetron sputtering deposition, which allows a wide range of control of chemical composition, crystallinity, and defect concentration. Additional to Ta3N5, this work also obtained a rarely reported Ta2N3 phase that adopts the Bixbyite structure. Detail characterization of structural, optical, and electrical properties of Ta2N3 are reported. Optimization of PEC performances of Ta3N5 and Ta2N3 thin films as photoanodes is achieved by adjusting deposition parameters. Improvement strategies for these emerging nitrides will also be discussed.