Understanding the mechanism of photochromism in double-layer metal oxide using X-ray photoelectron spectroscopy

Abstract We investigated the photochromism in a double-layer metal oxide by using X-ray photoelectron spectroscopy and scanning electron microscopy to identify the UV-induced reversible photochromism. We observed the metal oxide was reduced to a partially formed crystalline metal, and this was the cause of the photochromism. It was also found that this reduction induced by UV irradiation cracked the upper layer of magnesium-tin oxide and ultimately caused the reduced metal to oxidize slightly by being exposed to the atmosphere. This reversible transformation of a chemical species, on UV exposure, and discoloration induced by heating was considered to be a redox reaction.