Space variation of the crystallization kinetics in pure and mixed oxide films: A micro-Raman determination

Abstract

Abstract In several amorphous or nanocrystalline systems, the local heating associated with a focused laser beam of visible light induces a transformation towards ‘bulk crystal’ order. The various steps of this transformation can be monitored through the change in their Raman spectra, collected by a confocal microscope. In fact, these different steps of the evolution of the Raman spectra, reflecting different crystallization degrees, can be observed also as spatial variations by performing a Raman mapping on film samples that appear homogeneous under optical investigation. These variations, on the scale of micrometres, could reveal, in principle, the topography of the crystallinity of the film or the space variation of a ‘crystallization compliance’. These laser-induced transformations have been studied in transparent oxide films, having thickness of the order of a micrometre, obtained by different deposition techniques; here two examples are presented, concerning tungsten trioxide films made via sputtering techniques and mixed titanium oxide-vanadium oxide films deposited by a sol-gel method.