Chromium oxide formation on nanosecond and femtosecond laser irradiated thin chromium films

Thin coatings of Cr2O3 have been used for numerous applications. Selective oxidation of chromium will be beneficial for integrated device fabrications. Thin coatings of pure chromium were vacuum deposited on a glass substrate using hot electrons from tungsten filament. These coatings were then treated with nanosecond and femtosecond laser in ambient conditions. The microstructure, morphology and the color of the coatings treated with laser sources were modified and there was a formation of an oxide layer due to the heat dissipation on the chromium coating from the energetic photons. High-resolution scanning electron microscope studies showed the morphological evolution, which is directly correlated with the laser fluence of both the nanosecond and femtosecond lasers. This morphological evolution was accompanied by the microstructural change as observed from the X-ray diffraction patterns. The chromaticity response of the coating was studied by UV-Vis spectroscopy and the response of the coating in the visible region evolved with the laser fluences. The divergence in chromaticity of these two laser treatments, is due to the difference in morphology as the result of the varied pulse duration. It could be concluded that the morphology had effect on the chromaticity of the films. Futhermore, Rutherford backscattering depth profiling of the laser treated coatings revealed the diffusion of oxygen atoms in the coating as a result of laser treatment fluence. We have analyzed both the optical and material properties of the laser induced oxidation and demonstrated laser writing as a promising tool to selectively oxidize Chromium for integrated device applications.