New signature discovered characterizes structural defects in tin dichalcogenides

For applications from solar cells to batteries, layered chalcogenide semiconductors show promise in their ability to harvest and store energy. One family of abundant materials, tin sulfides and selenides, is of particular recent interest but so far has seen limited use because they can readily convert into phases with lower sulfur concentration by the introduction of sulfur vacancies.

A research team points to reliable methods for measuring these defects and could help move tin chalcogenide semiconductors toward energy applications. Appearing in Applied Physics Letters, the work describes the effects that defects in tin dichalcogenide crystals have on its luminescence, and the discovery of an optoelectronic signature that can be used to assess the quality of the semiconductors.

The authors subjected tin disulfide crystals to electron beam irradiation to induce sulfur vacancies, and examined the material’s optoelectronic features using in-situ cathodoluminescence spectroscopy. An electron microscope beam stimulated and imaged the progressive transformation of the tin disulfide to a less sulfur-rich phase by accumulation of sulfur vacancy defects. They then probed the ensuing changes of light emission at the nanometer scale.

By combining spectroscopy experiments with calculations, the team found the most prominent source of emission from samples with induced defects was the recombination of excitons bound to neutral sulfur vacancies within tin disulfide. The results represent an important step toward understanding how defects, which are invariably present in real-world materials, shape the optoelectronic properties of layered chalcogenide semiconductors.

Source: “Luminescence of defects in the structural transformation of layered tin dichalcogenides,” by P. Sutter, H.-P. Komsa, A. V. Krasheninnikov, Y. Huang, and E. Sutter, Applied Physics Letters (2017). The article can be accessed at https://doi.org/10.1063/1.5007060 .