Reactive laser interference patterning on titanium and zinc in high pressure CO₂

Direct laser interference patterning (DLIP) is a versatile technique for surface patterning that enables formation of micro-nano sized periodic structures on top of the target material. In this study, DLIP in high pressure, supercritical and liquid CO₂ by 4-beam DLIP was used to pattern titanium and zinc targets. Field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy was used to characterize the patterned surfaces. Field emission SEM analysis showed presence of ordered uniform donut ring pattern with hollow centers for both titanium and zinc with a period slightly under 3 µm while topographical images from atomic force microscopy revealed donut rings protruding outwards typically around 200 nm from target surface and consisted of a crevice at the center with a depth typically around 300 nm and 250 nm for titanium and zinc target, respectively. Based on X-ray photoelectron spectroscopic analysis, this is the first study to report formation of TiO₂, TiC, ZnCO₃, and zinc hydroxy carbonate on the pattern by DLIP in supercritical and liquid CO₂ for titanium and zinc targets. Pressurized CO₂ is demonstrated as a promising environment with mirror-based DLIP system for reactive patterning. Due to the superior transport properties and solvent power of supercritical CO₂, the current study opens possibilities for reactive patterning in environments that may not have been previously possible.