Florian Camilo, Déziel Jean-Luc, Kirner Sabrina V, Siegel Jan, Bonse Jörn
Bundesanstalt für Materialforschung und -prüfung (B A M), Unter den Eichen 87, 12205 Berlin, Germany.
Département de Physique, Université Laval, Pavillon Alexandre-Vachon 1045, Av. de la Médecine, G1V0A6 Québec, Canada.
Nanomaterials (Basel). 2020 Jan 14;10(1):147. doi: 10.3390/nano10010147.
Laser-induced periodic surface structures (LIPSS) are often present when processing solid targets with linearly polarized ultrashort laser pulses. The different irradiation parameters to produce them on metals, semiconductors and dielectrics have been studied extensively, identifying suitable regimes to tailor its properties for applications in the fields of optics, medicine, fluidics and tribology, to name a few. One important parameter widely present when exposing the samples to the high intensities provided by these laser pulses in air environment, that generally is not considered, is the formation of a superficial laser-induced oxide layer. In this paper, we fabricate LIPSS on a layer of the oxidation prone hard-coating material chromium nitride in order to investigate the impact of the laser-induced oxide layer on its formation. A variety of complementary surface analytic techniques were employed, revealing morphological, chemical and structural characteristics of well-known high-spatial frequency LIPSS (HSFL) together with a new type of low-spatial frequency LIPSS (LSFL with an anomalous orientation parallel to the laser polarization. Based on this input, we performed finite-difference time-domain calculations considering a layered system resembling the geometry of the HSFL along with the presence of a laser-induced oxide layer. The simulations support a scenario that the new type of LSFL is formed at the interface between the laser-induced oxide layer and the non-altered material underneath. These findings suggest that LSFL structures parallel to the polarization can be easily induced in materials that are prone to oxidation.
当用线偏振超短激光脉冲处理固体靶材时，通常会出现激光诱导周期性表面结构（LIPSS）。人们已经广泛研究了在金属、半导体和电介质上产生这些结构的不同辐照参数，确定了合适的条件来调整其特性，以应用于光学、医学、流体力学和摩擦学等领域，仅举几例。在空气环境中，当将样品暴露于这些激光脉冲提供的高强度下时，一个普遍未被考虑的重要参数是表面激光诱导氧化层的形成。在本文中，我们在易氧化的硬涂层材料氮化铬层上制备了LIPSS，以研究激光诱导氧化层对其形成的影响。我们采用了多种互补的表面分析技术，揭示了众所周知的高空间频率LIPSS（HSFL）以及一种新型的低空间频率LIPSS（LSFL，其取向异常平行于激光偏振）的形态、化学和结构特征。基于这些数据，我们进行了时域有限差分计算，考虑了一个类似于HSFL几何形状的分层系统以及激光诱导氧化层的存在。模拟结果支持了一种情况，即新型LSFL是在激光诱导氧化层与下方未改变材料的界面处形成的。这些发现表明，在易氧化的材料中可以很容易地诱导出平行于偏振的LSFL结构。
