Photo-Switchable Nanoripples in Ti₃C₂<i>T</i>_<i>x</i> MXene

MXenes are two-dimensional materials with a rich set of chemical and electromagnetic properties, the latter including saturable absorption intense surface plasmon resonances. To fully harness functionality for applications in optics, electronics, sensing, it is important to understand interaction light on atomic femtosecond dimensions. Here, we use ultrafast electron diffraction high-resolution microscopy investigate laser-induced structural dynamics Ti3C2Tx nanosheets. We find an exceptionally fast lattice response electron-phonon coupling time 230 fs. Repetitive laser excitation transforms through transition into metamaterial deeply sub-wavelength nanoripples that aligned polarization. By further illumination, material reversibly photo-switchable between flat rippled morphology. The resulting nanostructured MXene directional expected exhibit anisotropic optical electronic as well enhanced activity can be switched off by light.