Photochromic response of the PLD-grown nanostructured MoO3 thin films

Abstract

We have studied the PLD-grown nanostructured MoO3 thin film for its photochromic performance. MoO3 nanostructures were grown at room-temperature using PLD technique and subsequently annealed at 573 K. The annealedMoO3 films are then characterized by Raman spectroscopic study. The Raman spectra showed two strong peaks at 819 and 994 cm−1 due to the vibrations of the O-Mo6+-O and Mo6+-O bonds, respectively. Here, the peak at 994 cm−1 is ascribed to the terminal oxygen stretching mode for orthorhombic MoO3. Here, LASER power dependence on the Raman spectroscopic study was also done. Notably, the Raman peak is found to shift to low-frequency with increasing LASER power, most likely due to the coloration process which is attributed to variation in the Mo-O bond strengths and bond length in the nanocrystalline MoO3. The CAFM studies on the grown MoO3 nanostructures with LASER-ON and –OFF conditions were carried out at the various DC bias voltages from 10 V to −10 V. This study reveals that the MoO3 NS exhibits enhanced photochromic response. That is, with the LASER-ON, the Mo5+ states are generated due to the reduction of the Mo6+ states with induced electron incorporation by the LASER. The reduction leads to the transition from the Mo6+ to Mo5+, which obviously seen in the Raman data. As a consequence, the PLD-grown MoO3 nanostructures show a photochromic behavior.