Ultrafast laser writing structural colors on TiAlN-TiN hybrid films

We experimentally demonstrate ultrafast laser-writing wide-gamut structural colors on TiAlN thin film that is coated on TiN substrate via laser-induced surface oxidation. The experiments involve thorough control over laser parameters, including powers, scanning speeds and pulse durations, to investigate the interplay between these variables and the resulting structural colors. Surface characterization techniques, such as scanning electron microscopy, energy-dispersive x-ray spectroscopy and atomic force microscopy, are employed to analyze the properties of laser-induced oxide layers and their chromatic responses. Our findings indicate that while laser powers and scanning speeds are critical in determining the irradiated dose and the subsequent coloring effects, the pulse duration exerts a distinct influence, particularly at low laser powers as well as slow scanning speeds. Longer pulse durations are found to produce a more significant coloring change despite exhibiting lower oxygen content. This is attributed to the increased surface roughness and deeper oxidation layer achieved with prolonged pulses. We propose two oxidation mechanisms – photo-oxidation and thermal-oxidation – to elucidate the influence of pulse duration on laser coloring effects. These findings not only refine existing paradigms in laser-induced surface coloration but also stimulate further exploration of structural colors’ multifaceted applications across diverse technological contexts.