The Role of the Laser-Induced Oxide Layer in the Formation of Laser-Induced Periodic Surface Structures

Abstract

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.

Maxwell Meets Marangoni—A Review of Theories on Laser‐Induced Periodic Surface Structures

“…With the help of FDTD, even more complex situations than surfaces of different classes of bulk materials can be investigated. This was recently demonstrated by Florian et al., [ 95 ] who investigated the impact of a (laser‐induced) oxide layer formed at the surface of oxidation prone, strongly absorbing materials (such as a CrN ceramic, see Figure ). It was demonstrated experimentally and by FDTD simulations that an oxide layer of ≈100 nm thickness strongly influences the formation of a regular intensity pattern at the interface to the underlying material that finally leads to the formation of the interfacial LSFL‐II structures parallel to the laser beam polarization.…”

“…Reproduced under the terms of a Creative Commons BY 4.0 license. [ 95 ] Copyright 2020, The Authors, published by MDPI.…”

Quo Vadis LIPSS?—Recent and Future Trends on Laser-Induced Periodic Surface Structures

“…It is triggered by the fact that many applications of LIPSS, e.g., for surface wetting control, cell and bacterial adhesion, or the management of friction and wear, are affected by both the sample topography and the local surface chemistry. While most of the early research focused mainly on topographical effects, currently, the influence of the surface chemistry is increasingly investigated [ 9 , 36 , 37 , 38 , 39 ], studying, in detail, superficial oxidation upon irradiation in air environment and post-irradiation molecular adsorption phenomena.…”

Hierarchical Micro-/Nano-Structures on Polycarbonate via UV Pulsed Laser Processing

“…Several types of LIPSS can be distinguished, depending on the laser processing parameters and the material, e.g., common Low Spatial Frequency LIPSS (LSFL) with a period of about the laser wavelength ( ), High Spatial Frequency LIPSS (HSFL) with a period well below the laser wavelength ( ), or even hexagonally arranged triangular nanopillars with an overall period close to the laser wavelength ( ) [ 25 , 28 ]. LIPSS can be processed on metals [ 8 , 9 , 10 , 18 , 19 , 20 , 29 ], semiconductors [ 12 , 21 , 25 , 28 ], dielectrics [ 30 ], ceramics [ 31 , 32 , 33 ] and polymers [ 34 , 35 , 36 , 37 ]. Large area processing of LIPSS is easily achieved in a one-step approach by scanning the focused laser beam in a meandering way across the sample surface.…”