Influence of post-annealing on the structure and optical properties of ITO nanocrystals prepared by electrochemical method

We report the influence of post-annealing treatment on the structure and optical properties of ITO nanopowders prepared by electrochemical method. We found that the as-prepared two-phase ITO nanocrystals can transform to pure cubic structure after annealing at 600 °C in N2 atmosphere. The average crystal size increases with increasing annealing temperature and is about 60 nm at 800 °C. The optical band gap of the ITO nanocrystals increases with increasing annealing temperature. The reflectance of the ITO nanocrystals increases rapidly at near ultraviolet region and reaches maximum at visible light region, and then gradually decreases till near infrared region. And the annealed ITO nanocrystals show an excellent blocking effect in the wavelength range of 2.5–5 μm. The reason of the blue shift of the optical band gap and the odd reflectance behaviors were analyzed and discussed.

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► Cubic ITO nanocrystals with an average size of 30 nm are formed by annealing ITO precursors at 600 °C in N2 atmosphere.
► Optical band gap of ITO nanocrystals increases with increasing annealing temperature.
► Reflectance of ITO nanocrystals firstly increases and then gradually decreases with wavelength.
► ITO nanocrystals show an excellent blocking effect in the wavelength range of 2.5–5 μm.