Apr 8, 2025
5:00pm - 7:00pm
Summit, Level 2, Flex Hall C
Anja Tiede1,Raphael Lemerle1,Thomas Hagger1,Helena Rabelo2,Maria Chiara Spadaro2,3,4,Jordi Arbiol2,Anna Fontcuberta i Morral1
Ecole Polytechnique Federale de Lausanne1,Catalan Institute of Nanoscience and Nanotechnology2,Università degli Studi di Catania3,Institute for Microsystems and Microelectronics IMM4
Anja Tiede1,Raphael Lemerle1,Thomas Hagger1,Helena Rabelo2,Maria Chiara Spadaro2,3,4,Jordi Arbiol2,Anna Fontcuberta i Morral1
Ecole Polytechnique Federale de Lausanne1,Catalan Institute of Nanoscience and Nanotechnology2,Università degli Studi di Catania3,Institute for Microsystems and Microelectronics IMM4
Zinc phosphide is a novel, earth-abundant material that is promising as photovoltaic absorber for thin film devices because of its direct bandgap of 1.5 eV, high absorption coefficient in the visible range and high carrier diffusion length. In the past, obtaining reproducible characterization results of zinc phosphide has been a challenge owing to the different fabrication methods, crystallinities and compositions of the material. It was also speculated that the material would be unstable as a result of reaction with ambient water vapor and/or oxygen.
Here, we present a long-term study on how exposure to atmosphere impacts high-quality, monocrystalline zinc phosphide thin films obtained by molecular beam epitaxy. Using different experimental techniques like ellipsometry, Raman spectroscopy, X-ray diffraction measurements, transmission electron microscopy and secondary ion mass spectroscopy, we elucidate the significant effect oxidation has on the composition of the thin film at the surface, extending well into the bulk of the film. Moreover, we show that this degradation happens only under atmospheric conditions.
Finally, we demonstrate that the degradation can be prevented by utilizing a dielectric as thin protective layer or simply by keeping the unprotected thin films under vacuum. Our study highlights the importance of storage conditions for crystalline zinc phosphide thin films prior to the fabrication of photovoltaic devices.