Refraction index and oscillator strength in MoO3 photocolored films

Amorphous MoO3 films were grown onto glass substrates by the thermal evapor ation technique. Color centers in the films were generated by UV-VIS light irradiation (photochromism) in air at room temperature. As-grown films look ed pale yellowish to naked eye and acquired a bluish tone after the colorat ion process. Refraction index and extinction coefficient were calculated on as-grown and colored samples by using macroscopic optical differential ref lectance measurements fitted with the transfer matrix theoretical model. Th e coloration efficiency parameter and the refraction index values of MoO3 f ilms allowed us to calculate the oscillator strength (f) value equal to 0.2 2 +/- 0.02 by means of the optical absorption spectra. This value was obtai ned by fitting the experimental results to an optional expression of Smakul a's formula, derived from a semi-classical theoretical model. (C) 1999 Else vier Science B.V. All rights reserved.