Thermal modification of MoO3 nanofilms

Optical spectroscopy results demonstrate that heat treatment of 2- to 60-nm-thick MoO3 films for 1 s to 120 min in the temperature range 573-873 K reduces their absorbance in the range lambda = 300-480 nm (lambda(max) = 350 nm) and increases it in the range lambda = 480-1100 nm (lambda(max) = 870 nm). The degree of conversion of the MoO3 films increases with increasing heat-treatment time and temperature and with decreasing film thickness. A mechanism is proposed for the thermal modification of MoO3 films, which involves the formation of a [(V (a))(++) e] center during the preparation of the MoO3 film and a thermally activated electron transition from the valence band to the level of the [(V (a))(++) e] center, resulting in the formation of an [e (V (a))(++) e] center.