Laser‐Induced Periodic TiO 2 Nanostructures for Enhanced Ethanol Gas Sensing

Controlled exposure of specific crystal facets in metal oxide nanomaterials holds great potential for surface/interface applications yet remains challenging due to difficulties in modulating surface energy. Here, femtosecond laser‐induced periodic surface structures (LIPSS) were fabricated on TiO 2 epitaxial thin films with precise control over the exposed facet orientation. Highly regular subwavelength one‐dimensional LIPSS exhibited a period of 130 ± 15 nm, a width of 85 ± 10 nm, and a depth of 105 ± 5 nm. By adjusting the laser polarization direction relative to the crystallographic orientation of the epitaxial TiO 2 film, the LIPSS alignment could be directed along different crystal orientations. Ethanol gas‐sensing tests on TiO 2 LIPSS structures aligned with different crystal orientations demonstrated that the nanostructures increased surface area, thereby enhancing gas‐sensing response. Compared to TiO 2 films with LIPSS along the {110} crystal facets, those along the high‐energy {100} facets showed superior gas‐sensing performance, underscoring the critical role of high‐energy facets in boosting surface reactivity and response. This approach offers a novel method and theoretical basis for enhancing gas sensor performance, facilitating broader adoption of TiO 2 ‐based sensors in environmental monitoring and related applications.