Arsenic selenide thin film degradation and its mitigation

Thin films of arsenic triselenide (As2Se3) glass degrade significantly under ambient conditions in the presence of light. We investigate the mechanism of this degradation by maintaining thin film As2Se3 samples in a variety of environmental conditions for approximately one year and show that exposure to below-band gap light in the presence of oxygen and moisture lead to the formation of crystallites of arsenic oxide and selenium. Spectroscopic measurements, X-ray diffraction (XRD), and microscopy reveal that deposition of a thin (~10 nm) passivation layer together with preventing exposure to below-band gap light inhibits degradation. These results indicate that As2Se3 is a practical material for use in applications such as integrated optic waveguides or dielectric metasurfaces operating in wavelengths from the short-wave infrared through the long-wave infrared.