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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Selective femtosecond laser ablation of graphene for its micro-patterning
摘要： Due to the outstanding electrical properties of graphene, the demand of its clean and well-defined micro-structures for diverse applications has increased. However, such micro-structured graphene is difficult due to handling and machining problems. Femtosecond lasers are versatile tools for controlled ablation and resulting patterning process. In this paper, we present the selective ablation and functionalization of monolayers of graphene on 300 nm thick thermally grown silicon dioxide on silicon substrates with a Ti:sapphire laser (λ = 800 nm, τ = 40 fs). Investigations were performed on the micro-patterns in graphene ablated by the laser in the fluence range of 0.9-2.2 J/cm2. Just below the ablation threshold functionalization of the graphene layer was obtained. The resolution of the patterning was in the range of a few micrometers. In order to study the effect of oxidation of graphene at the ablation rim, the experiments were conducted both under ambient and inert gas atmosphere conditions. The morphology of the irradiated region of graphene was evaluated with optical microscopy, scanning electron microscopy and atomic force microscopy. With Raman spectroscopy the complete removal of graphene was ascertained. Finally, we find that femtosecond laser ablation is a promising method for direct writing of micro-patterns in graphene monolayers for various potential applications, e.g. for electrodes of thin film transistors.
关键词： selective ablation,functionalization,femtosecond laser ablation,micro-patterning,graphene
更新于2025-09-11 14:15:04
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Growth Promotion of Targeted Crystal Face by Nano-Processing via Laser Ablation
摘要： Control of crystal shape is an indispensable step for various applications of crystalline products. However, obtaining the desired crystal shape by conventionally tuning environmental conditions (temperature, additives, etc.) cannot always be reached. Recently, we have developed an innovative approach for spatiotemporal control of crystal growth of proteins and amino acids by locally modifying crystal structure (e.g., formation of screw dislocations) via femtosecond (fs) laser ablation. In this work, to clarify the appropriate laser condition for controlling the shape of single crystals with minimized damage, we first systematically investigated the dependence of pulse duration on laser ablation and crystal growth of L-phenylalanine (L-Phe). By using a laser system with tunable pulse durations from fs to nanosecond (ns), we found fs laser ablation can offer nanometer-sized, sharp etching of which diameter was smaller than the diffraction limit. By utilizing such nano-processing via fs laser ablation for promoting the growth of a targeted crystal face, we successfully demonstrated the preparation of a bulky crystal of L-Phe, which are difficult to be obtained by conventional crystallization methods.
关键词： L-phenylalanine,nano-processing,single crystal growth,crystal shape control,femtosecond laser ablation
更新于2025-09-11 14:15:04
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Femtosecond-laser-ablation induced transformations in the structure and surface properties of diamond-like nanocomposite films
摘要： Femtosecond laser ablation processing is applied for surface modification and micropatterning of diamond-like nanocomposite (DLN) films (a-C:H:Si:O films). Using a visible femtosecond laser (wavelength 515 nm, pulse duration 320 fs), microgroove patterns have been fabricated on the DLN films, aimed at further studies of their properties. The studies were focused on (i) structural transformations in the surface layers using Raman spectroscopy and transmission electron microscopy (TEM), (ii) wettability of laser-patterned films, and (iii) nano/microscale friction properties of laser-patterned DLN films using lateral force microscopy. Raman spectroscopy and TEM data showed characteristic features of the surface graphitization during ultrashort-pulse ablation. High resolution TEM study of the microgrooves revealed the formation of cubic SiC nanocrystals (4–8 nm size) on the laser-ablated surface. The water contact angle measurements showed anisotropic wetting behavior of the grooved surfaces (the contact angle was different in the directions parallel and perpendicular to microgrooves), depending on the groove depth (aspect ratio). Lateral force microscopy examination (with micro-sized Si tips) showed that the laser-patterned regions exhibited low friction properties compared to the original surface. The obtained results demonstrate that femtosecond laser processing is an effective technique to generate new properties of hard DLN coatings at the micro and macroscale.
关键词： Diamond-like nanocomposite films,Femtosecond laser ablation,Micropatterning,SiC nanocrystals,Graphitization,Wettability
更新于2025-09-11 14:15:04