Pimenov Sergei M, Zavedeev Evgeny V, Jaeggi Beat, Zuercher Josef, Neuenschwander Beat
Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia.
Institute for Applied Laser, Photonics and Surface Technologies ALPS, Bern University of Applied Sciences, CH-3400 Burgdorf, Switzerland.
Materials (Basel). 2022 Jun 26;15(13):4506. doi: 10.3390/ma15134506.
In the paper, we study the formation of laser-induced periodic surface structures (LIPSS) on diamond-like nanocomposite (DLN) a-C:H:Si:O films during nanoscale ablation processing at low fluences-below the single-pulse graphitization and spallation thresholds-using an IR fs-laser (wavelength 1030 nm, pulse duration 320 fs, pulse repetition rate 100 kHz, scanning beam velocity 0.04-0.08 m/s). The studies are focused on microscopic analysis of the nanostructured DLN film surface at different stages of LIPSS formation and numerical modeling of surface plasmon polaritons in a thin graphitized surface layer. Important findings are concerned with (i) sub-threshold fabrication of high spatial frequency LIPSS (HSFL) and low spatial frequency LIPSS (LSFL) under negligible surface graphitization of hard DLN films, (ii) transition from the HSFL (periods of 140 ± 30 and 230 ± 40 nm) to LSFL (period of 830-900 nm) within a narrow fluence range of 0.21-0.32 J/cm, (iii) visualization of equi-field lines by ablated nanoparticles at an initial stage of the LIPSS formation, providing proof of larger electric fields in the valleys and weaker fields at the ridges of a growing surface grating, (iv) influence of the thickness of a laser-excited glassy carbon (GC) layer on the period of surface plasmon polaritons excited in a three-layer system "air/GC layer/DLN film".
在本文中，我们研究了在低能量密度（低于单脉冲石墨化和层裂阈值）下，使用红外飞秒激光（波长1030 nm，脉冲持续时间320 fs，脉冲重复频率100 kHz，扫描光束速度0.04 - 0.08 m/s）对类金刚石纳米复合材料（DLN）a-C:H:Si:O薄膜进行纳米级烧蚀处理时激光诱导周期性表面结构（LIPSS）的形成。研究重点是LIPSS形成不同阶段纳米结构DLN薄膜表面的微观分析以及薄石墨化表面层中表面等离子体激元的数值模拟。重要发现包括：（i）在硬DLN薄膜表面石墨化可忽略不计的情况下，亚阈值制备高空间频率LIPSS（HSFL）和低空间频率LIPSS（LSFL）；（ii）在0.21 - 0.32 J/cm的窄能量密度范围内，从HSFL（周期为140 ± 30和230 ± 40 nm）转变为LSFL（周期为830 - 900 nm）；（iii）在LIPSS形成初期，通过烧蚀纳米颗粒可视化等场线，证明生长表面光栅谷底电场较大而脊顶电场较弱；（iv）激光激发的玻璃碳（GC）层厚度对三层系统“空气/GC层/DLN薄膜”中激发的表面等离子体激元周期的影响。
