Volkov Mikhail, Willinger Elena, Kuznetsov Denis A, Müller Christoph R, Fedorov Alexey, Baum Peter
University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany.
Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany.
ACS Nano. 2021 Sep 28;15(9):14071-14079. doi: 10.1021/acsnano.1c03635. Epub 2021 Aug 31.
MXenes are two-dimensional materials with a rich set of chemical and electromagnetic properties, the latter including saturable absorption and intense surface plasmon resonances. To fully harness the functionality of MXenes for applications in optics, electronics, and sensing, it is important to understand the interaction of light with MXenes on atomic and femtosecond dimensions. Here, we use ultrafast electron diffraction and high-resolution electron microscopy to investigate the laser-induced structural dynamics of TiC nanosheets. We find an exceptionally fast lattice response with an electron-phonon coupling time of 230 fs. Repetitive femtosecond laser excitation transforms TiC through a structural transition into a metamaterial with deeply sub-wavelength nanoripples that are aligned with the laser polarization. By a further laser illumination, the material is reversibly photo-switchable between a flat and rippled morphology. The resulting nanostructured MXene metamaterial with directional nanoripples is expected to exhibit an anisotropic optical and electronic response as well as an enhanced chemical activity that can be switched on and off by light.
MXenes是具有丰富化学和电磁特性的二维材料，后者包括可饱和吸收和强烈的表面等离子体共振。为了充分利用MXenes在光学、电子和传感领域的应用功能，了解光与MXenes在原子和飞秒尺度上的相互作用非常重要。在这里，我们使用超快电子衍射和高分辨率电子显微镜来研究激光诱导的TiC纳米片的结构动力学。我们发现了异常快速的晶格响应，电子-声子耦合时间为230飞秒。重复的飞秒激光激发通过结构转变将TiC转变为具有与激光偏振方向一致的深亚波长纳米波纹的超材料。通过进一步的激光照射，该材料可以在平坦和波纹形态之间可逆地光开关。由此产生的具有定向纳米波纹的纳米结构MXene超材料预计将表现出各向异性的光学和电子响应以及增强的化学活性，并且可以通过光进行开关。
