1
|
Florian C, Fuentes-Edfuf Y, Skoulas E, Stratakis E, Sanchez-Cortes S, Solis J, Siegel J. Influence of Heat Accumulation on Morphology Debris Deposition and Wetting of LIPSS on Steel upon High Repetition Rate Femtosecond Pulses Irradiation. MATERIALS (BASEL, SWITZERLAND) 2022; 15:7468. [PMID: 36363059 PMCID: PMC9656394 DOI: 10.3390/ma15217468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/18/2022] [Accepted: 10/20/2022] [Indexed: 06/16/2023]
Abstract
The fabrication of laser-induced periodic surface structures (LIPSS) over extended areas at high processing speeds requires the use of high repetition rate femtosecond lasers. It is known that industrially relevant materials such as steel experience heat accumulation when irradiated at repetition rates above some hundreds of kHz, and significant debris redeposition can take place. However, there are few studies on how the laser repetition rate influences both the debris deposition and the final LIPSS morphology. In this work, we present a study of fs laser-induced fabrication of low spatial frequency LIPSS (LSFL), with pulse repetition rates ranging from 10 kHz to 2 MHz on commercially available steel. The morphology of the laser-structured areas as well as the redeposited debris was characterized by scanning electron microscopy (SEM) and µ-Raman spectroscopy. To identify repetition rate ranges where heat accumulation is present during the irradiations, we developed a simple heat accumulation model that solves the heat equation in 1 dimension implementing a Forward differencing in Time and Central differencing in Space (FTCS) scheme. Contact angle measurements with water demonstrated the influence of heat accumulation and debris on the functional wetting behavior. The findings are directly relevant for the processing of metals using high repetition rate femtosecond lasers, enabling the identification of optimum conditions in terms of desired morphology, functionality, and throughput.
Collapse
Affiliation(s)
- Camilo Florian
- Instituto de Óptica (IO-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 121, 28006 Madrid, Spain
| | - Yasser Fuentes-Edfuf
- Instituto de Óptica (IO-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 121, 28006 Madrid, Spain
| | - Evangelos Skoulas
- Instituto de Estructura de la Materia (CSIC), Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid, Spain
| | - Emmanuel Stratakis
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH), N. Plastira 100, Vassilika Vouton, 70013 Heraklion, Greece
| | - Santiago Sanchez-Cortes
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH), N. Plastira 100, Vassilika Vouton, 70013 Heraklion, Greece
| | - Javier Solis
- Instituto de Óptica (IO-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 121, 28006 Madrid, Spain
| | - Jan Siegel
- Instituto de Óptica (IO-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 121, 28006 Madrid, Spain
| |
Collapse
|
2
|
Research on Monocrystalline Silicon Micro-Nano Structures Irradiated by Femtosecond Laser. MATERIALS 2022; 15:ma15144897. [PMID: 35888363 PMCID: PMC9317364 DOI: 10.3390/ma15144897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/27/2022] [Accepted: 07/08/2022] [Indexed: 11/17/2022]
Abstract
Femtosecond (fs) laser processing has received great attention for preparing novel micro-nano structures and functional materials. However, the induction mechanism of the micro-nano structures induced by fs lasers still needs to be explored. In this work, the laser-induced periodic surface structure (LIPSS) of monocrystalline silicon (Si) under fs laser irradiation is investigated. Three different layers named amorphous silicon (a-Si) layer, transition layer, and unaffected Si layer are observed after laser irradiation. The a-Si layer on the surface is generated by the resolidification of melting materials. The unaffected Si layer is not affected by laser irradiation and maintains the initial atomic structure. The transition layer consisting of a-Si and unaffected Si layers was observed under the irradiated subsurface. The phase transition mechanism of Si irradiated by fs laser is “amorphous transition”, with the absence of other crystal structures. A numerical model is established to describe the fs laser-Si interaction to characterize the electronic (lattice) dynamics of the LIPSS formation. The obtained results contribute to the understanding of fs laser processing of Si at the atomic scale as well as broaden the application prospects of fs laser for treating other semiconductor materials.
Collapse
|
3
|
Nykyruy Y, Mudry S, Shtablavyi I, Gnilitskyi I. Nanostructuring of Fe73.5Nb3Cu1Si15.5B7 amorphous alloy surface by laser-induced periodic structure formation. APPLIED NANOSCIENCE 2022. [DOI: 10.1007/s13204-021-01866-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
4
|
Mastellone M, Pace ML, Curcio M, Caggiano N, De Bonis A, Teghil R, Dolce P, Mollica D, Orlando S, Santagata A, Serpente V, Bellucci A, Girolami M, Polini R, Trucchi DM. LIPSS Applied to Wide Bandgap Semiconductors and Dielectrics: Assessment and Future Perspectives. MATERIALS 2022; 15:ma15041378. [PMID: 35207919 PMCID: PMC8880014 DOI: 10.3390/ma15041378] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 02/04/2022] [Accepted: 02/09/2022] [Indexed: 02/04/2023]
Abstract
With the aim of presenting the processes governing the Laser-Induced Periodic Surface Structures (LIPSS), its main theoretical models have been reported. More emphasis is given to those suitable for clarifying the experimental structures observed on the surface of wide bandgap semiconductors (WBS) and dielectric materials. The role played by radiation surface electromagnetic waves as well as Surface Plasmon Polaritons in determining both Low and High Spatial Frequency LIPSS is briefly discussed, together with some experimental evidence. Non-conventional techniques for LIPSS formation are concisely introduced to point out the high technical possibility of enhancing the homogeneity of surface structures as well as tuning the electronic properties driven by point defects induced in WBS. Among these, double- or multiple-fs-pulse irradiations are shown to be suitable for providing further insight into the LIPSS process together with fine control on the formed surface structures. Modifications occurring by LIPSS on surfaces of WBS and dielectrics display high potentialities for their cross-cutting technological features and wide applications in which the main surface and electronic properties can be engineered. By these assessments, the employment of such nanostructured materials in innovative devices could be envisaged.
Collapse
Affiliation(s)
- Matteo Mastellone
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
| | - Maria Lucia Pace
- ISM-CNR, FemtoLAB, U.O.S. Tito Scalo, Zona Industriale, 85050 Potenza, Italy; (M.L.P.); (P.D.); (D.M.); (S.O.)
| | - Mariangela Curcio
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (N.C.); (A.D.B.); (R.T.)
| | - Nicola Caggiano
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (N.C.); (A.D.B.); (R.T.)
| | - Angela De Bonis
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (N.C.); (A.D.B.); (R.T.)
| | - Roberto Teghil
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (N.C.); (A.D.B.); (R.T.)
| | - Patrizia Dolce
- ISM-CNR, FemtoLAB, U.O.S. Tito Scalo, Zona Industriale, 85050 Potenza, Italy; (M.L.P.); (P.D.); (D.M.); (S.O.)
| | - Donato Mollica
- ISM-CNR, FemtoLAB, U.O.S. Tito Scalo, Zona Industriale, 85050 Potenza, Italy; (M.L.P.); (P.D.); (D.M.); (S.O.)
| | - Stefano Orlando
- ISM-CNR, FemtoLAB, U.O.S. Tito Scalo, Zona Industriale, 85050 Potenza, Italy; (M.L.P.); (P.D.); (D.M.); (S.O.)
| | - Antonio Santagata
- ISM-CNR, FemtoLAB, U.O.S. Tito Scalo, Zona Industriale, 85050 Potenza, Italy; (M.L.P.); (P.D.); (D.M.); (S.O.)
- Correspondence: ; Tel.: +39-0971427227
| | - Valerio Serpente
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
| | - Alessandro Bellucci
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
| | - Marco Girolami
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
| | - Riccardo Polini
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
- Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma ‘Tor Vergata’, 00133 Rome, Italy
| | - Daniele Maria Trucchi
- ISM-CNR, DiaTHEMA Laboratory, U.O.S. Montelibretti, Via Salaria km 29.300, 00015 Monterotondo, Italy; (M.M.); (V.S.); (A.B.); (M.G.); (R.P.); (D.M.T.)
| |
Collapse
|
5
|
Girolami M, Bellucci A, Mastellone M, Orlando S, Serpente V, Valentini V, Polini R, Sani E, De Caro T, Trucchi DM. Femtosecond-Laser Nanostructuring of Black Diamond Films under Different Gas Environments. MATERIALS (BASEL, SWITZERLAND) 2020; 13:E5761. [PMID: 33348641 PMCID: PMC7766203 DOI: 10.3390/ma13245761] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 12/09/2020] [Accepted: 12/15/2020] [Indexed: 01/15/2023]
Abstract
Irradiation of diamond with femtosecond (fs) laser pulses in ultra-high vacuum (UHV) conditions results in the formation of surface periodic nanostructures able to strongly interact with visible and infrared light. As a result, native transparent diamond turns into a completely different material, namely "black" diamond, with outstanding absorptance properties in the solar radiation wavelength range, which can be efficiently exploited in innovative solar energy converters. Of course, even if extremely effective, the use of UHV strongly complicates the fabrication process. In this work, in order to pave the way to an easier and more cost-effective manufacturing workflow of black diamond, we demonstrate that it is possible to ensure the same optical properties as those of UHV-fabricated films by performing an fs-laser nanostructuring at ambient conditions (i.e., room temperature and atmospheric pressure) under a constant He flow, as inferred from the combined use of scanning electron microscopy, Raman spectroscopy, and spectrophotometry analysis. Conversely, if the laser treatment is performed under a compressed air flow, or a N2 flow, the optical properties of black diamond films are not comparable to those of their UHV-fabricated counterparts.
Collapse
Affiliation(s)
- Marco Girolami
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
| | - Alessandro Bellucci
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
| | - Matteo Mastellone
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
- Dipartimento di Scienze di Base ed Applicate per l’Ingegneria, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Stefano Orlando
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Tito Scalo, Area Industriale–Contrada S. Loia, Tito Scalo, 85050 Potenza, Italy;
| | - Valerio Serpente
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
| | - Veronica Valentini
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
| | - Riccardo Polini
- Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy;
| | - Elisa Sani
- Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO–CNR), Largo E. Fermi, 50125 Firenze, Italy;
| | - Tilde De Caro
- Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche (ISMN–CNR), Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy;
| | - Daniele M. Trucchi
- DiaTHEMA Lab, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM–CNR), Sede Secondaria di Montelibretti, Via Salaria km 29,300, Monterotondo Stazione, 00015 Roma, Italy; (A.B.); (M.M.); (V.S.); (V.V.); (D.M.T.)
| |
Collapse
|
6
|
Bonse J. Quo Vadis LIPSS?-Recent and Future Trends on Laser-Induced Periodic Surface Structures. NANOMATERIALS 2020; 10:nano10101950. [PMID: 33007873 PMCID: PMC7601024 DOI: 10.3390/nano10101950] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/24/2020] [Accepted: 09/29/2020] [Indexed: 02/06/2023]
Abstract
Nanotechnology and lasers are among the most successful and active fields of research and technology that have boomed during the past two decades. Many improvements are based on the controlled manufacturing of nanostructures that enable tailored material functionalization for a wide range of industrial applications, electronics, medicine, etc., and have already found entry into our daily life. One appealing approach for manufacturing such nanostructures in a flexible, robust, rapid, and contactless one-step process is based on the generation of laser-induced periodic surface structures (LIPSS). This Perspective article analyzes the footprint of the research area of LIPSS on the basis of a detailed literature search, provides a brief overview on its current trends, describes the European funding strategies within the Horizon 2020 programme, and outlines promising future directions.
Collapse
Affiliation(s)
- Jörn Bonse
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
| |
Collapse
|
7
|
Gurevich EL, Levy Y, Bulgakova NM. Three-Step Description of Single-Pulse Formation of Laser-Induced Periodic Surface Structures on Metals. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1836. [PMID: 32937947 PMCID: PMC7559113 DOI: 10.3390/nano10091836] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 11/16/2022]
Abstract
Two different scenarios are usually invoked in the formation of femtosecond Laser-Induced Periodic Surface Structures (LIPSS), either "self-organization" mechanisms or a purely "plasmonic" approach. In this paper, a three-step model of formation of single-laser-shot LIPSS is summarized. It is based on the periodic perturbation of the electronic temperature followed by an amplification, for given spatial periods, of the modulation in the lattice temperature and a final possible relocation by hydrodynamic instabilities. An analytical theory of the evolution of the temperature inhomogeneities is reported and supported by numerical calculations on the examples of three different metals: Al, Au, and Mo. The criteria of the possibility of hydrodynamic instabilities are also discussed.
Collapse
Affiliation(s)
- Evgeny L. Gurevich
- Laser Center (LFM), University of Applied Sciences Münster, Stegerwaldstraße 39, 48565 Steinfurt, Germany
| | - Yoann Levy
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 2524 Dolní Břežany, Czech Republic;
| | - Nadezhda M. Bulgakova
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 2524 Dolní Břežany, Czech Republic;
| |
Collapse
|
8
|
Kunz C, Engel S, Müller FA, Gräf S. Large-Area Fabrication of Laser-Induced Periodic Surface Structures on Fused Silica Using Thin Gold Layers. NANOMATERIALS 2020; 10:nano10061187. [PMID: 32570904 PMCID: PMC7353452 DOI: 10.3390/nano10061187] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 06/11/2020] [Accepted: 06/17/2020] [Indexed: 12/14/2022]
Abstract
Despite intensive research activities in the field of laser-induced periodic surface structures (LIPSS), the large-area nanostructuring of glasses is still a challenging problem, which is mainly caused by the strongly non-linear absorption of the laser radiation by the dielectric material. Therefore, most investigations are limited to single-spot experiments on different types of glasses. Here, we report the homogeneous generation of LIPSS on large-area surfaces of fused silica using thin gold layers and a fs-laser with a wavelength λ = 1025 nm, a pulse duration τ = 300 fs, and a repetition frequency frep = 100 kHz as radiation source. For this purpose, single-spot experiments are performed to study the LIPSS formation process as a function of laser parameters and gold layer thickness. Based on these results, the generation of large-area homogenous LIPSS pattern was investigated by unidirectional scanning of the fs-laser beam across the sample surface using different line spacing. The nanostructures are characterized by a spatial period of about 360 nm and a modulation depth of around 160 nm. Chemical surface analysis by Raman spectroscopy confirms a complete ablation of the gold film by the fs-laser irradiation. The characterization of the functional properties shows an increased transmission of the nanostructured samples accompanied by a noticeable change in the wetting properties, which can be additionally modified within a wide range by silanization. The presented approach enables the reproducible LIPSS-based laser direct-writing of sub-wavelength nanostructures on glasses and thus provides a versatile and flexible tool for novel applications in the fields of optics, microfluidics, and biomaterials.
Collapse
|
9
|
The Role of the Laser-Induced Oxide Layer in the Formation of Laser-Induced Periodic Surface Structures. NANOMATERIALS 2020; 10:nano10010147. [PMID: 31947575 PMCID: PMC7022235 DOI: 10.3390/nano10010147] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/06/2020] [Accepted: 01/09/2020] [Indexed: 11/17/2022]
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.
Collapse
|
10
|
Weber FR, Kunz C, Gräf S, Rettenmayr M, Müller FA. Wettability Analysis of Water on Metal/Semiconductor Phases Selectively Structured with Femtosecond Laser-Induced Periodic Surface Structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14990-14998. [PMID: 31687824 DOI: 10.1021/acs.langmuir.9b02406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Femtosecond (fs) laser-induced periodic surface structures (LIPSS) were selectively generated on the surface of an Ag-Si alloy consisting of a metallic and a semiconducting phase. For this purpose, the alloy was irradiated with linearly polarized fs-laser pulses (τ = 300 fs, λ = 1025 nm, frep = 100 kHz) using a laser peak fluence F = 0.30 J/cm2. Due to the different light absorption behaviors of the semiconductor (Si) and the metal (Ag) phases that result in different ablation thresholds of the respective phases, pronounced LIPSS with a period of Λ ≈ 950 nm and a modulation depth of h ≈ 220 nm were generated solely on the Si phase. The alloy surface was characterized by scanning electron microscopy, optical microscopy, white-light interference microscopy, and atomic force microscopy before and after laser irradiation. The chemical analysis was carried out by energy-dispersive X-ray spectroscopy, revealing surface oxidation of the Si phase and no laser-induced chemical modification of the Ag phase. The surface wettability of the alloy was evaluated with distilled water and compared to those of the single constituents of the composites. After fs-laser irradiation, the surface is characterized by a reduced hydrophilic water contact angle. Furthermore, the alloy selectively structured with LIPSS revealed a droplet shape change due to the distinctly different contact angles on the Si (θ = 5°) and Ag (θ = 74°) phases. This phenomenon was evaluated and discussed by local contact angle analyses using a confocal laser scanning microscope and Rhodamine B dye. In addition, it was shown that the shape change due to different contact angles of the components allowed a targeted droplet movement on a macroscopic material boundary (Ag/Si) of the alloy. Selectively structured metal/semiconductor surfaces might be of particular interest for microfluidic devices with a directional droplet movement and for the fundamental research of wettability.
Collapse
Affiliation(s)
- Felix R Weber
- Otto Schott Institute of Materials Research (OSIM) , Friedrich Schiller University Jena , Löbdergraben 32 , 07743 Jena , Germany
| | - Clemens Kunz
- Otto Schott Institute of Materials Research (OSIM) , Friedrich Schiller University Jena , Löbdergraben 32 , 07743 Jena , Germany
| | - Stephan Gräf
- Otto Schott Institute of Materials Research (OSIM) , Friedrich Schiller University Jena , Löbdergraben 32 , 07743 Jena , Germany
| | - Markus Rettenmayr
- Otto Schott Institute of Materials Research (OSIM) , Friedrich Schiller University Jena , Löbdergraben 32 , 07743 Jena , Germany
| | - Frank A Müller
- Otto Schott Institute of Materials Research (OSIM) , Friedrich Schiller University Jena , Löbdergraben 32 , 07743 Jena , Germany
| |
Collapse
|