Nonequilibrium surface oxygen vacancy in MgTiO3 inducing fast optical transformation under laser irradiation

Point defect has a significant impact on the optical properties of materials. The light absorption behavior can be changed through adjusting the concentration of point defect. Here, nonequilibrium surface oxygen vacancy is firstly introduced into MgTiO 3 material and then eliminated under laser irradiation to realize an optical transformation from high absorption to high reflectivity among a wide range of wavelength. NaBH 4 low-temperature reduction treatment is conducted to control the distribution of oxygen vacancy. MgTiO 3 @MgTiO 3-x core-shell structure is fabricated through the treatment, in which disordered MgTiO 3-x with high-concentration of oxygen vacancy forms a shell covering a highly crystalline MgTiO 3 core. The reflectivity is reduced to 5 % among 400–2500 nm due to the interconduction subband absorption of the metallized disordered MgTiO 3-x shell. Research shows that the core-shell structure is beneficial for enhancing the transformation rate owing to the short diffusion distance. Remarkably, under 100 W cm −2 1064 nm laser irradiation, the nonequilibrium surface oxygen vacancy can be eliminated in a short time and the material will transform to high-reflectivity state in 1000 ms, with the reflectivity restoring to 83 %.