In situ monitoring of laser-induced periodic surface structures formation on polymer films by grazing incidence small-angle X-ray scattering

9 pags.; 9 figs.© 2015 American Chemical Society. The formation of laser-induced periodic surface structures (LIPSS) on model spin-coated polymer films has been followed in situ by grazing incidence small-angle X-ray scattering (GISAXS) using synchrotron radiation. The samples were irradiated at different repetition rates ranging from 1 up to 10 Hz by using the fourth harmonic of a Nd:YAG laser (266 nm) with pulses of 8 ns. Simultaneously, GISAXS patterns were acquired during laser irradiation. The variation of both the GISAXS signal with the number of pulses and the LIPSS period with laser irradiation time is revealing key kinetic aspects of the nanostructure formation process. By considering LIPSS as one-dimensional paracrystalline lattice and using a correlation found between the paracrystalline disorder parameter, g, and the number of reflections observed in the GISAXS patterns, the variation of the structural order of LIPSS can be assessed. The role of the laser repetition rate in the nanostructure formation has been clarified. For high pulse repetition rates (i.e., 10 Hz), LIPSS evolve in time to reach the expected period matching the wavelength of the irradiating laser. For lower pulse repetition rates LIPSS formation is less effective, and the period of the ripples never reaches the wavelength value. Results support and provide information on the existence of a feedback mechanism for LIPSS formation in polymer films.The authors gratefully acknowledge financial support from the MINECO (MAT2011-23455, MAT2012-33517 and CTQ 2013-43086-P). E.R., I.M.-F., and A.R-R. also thank MINECO for a Ramon y Cajal contract (RYC-2011-08069) and FPI ́ fellowships (BES-2010-030074 and BES-2013-062620).Peer Reviewe

Laser-Induced Periodic Surface Structures on Conjugated Polymers: Poly(3-hexylthiophene)

8 pags.; 11 figs.© 2015 American Chemical Society. In this work, we report on the surface patterning of semiconducting poly(3-hexylthiophene) (P3HT) thin films by means of laser-induced periodic surface structures (LIPSS). Two different laser wavelengths, 266 and 532 nm, and a broad range of fluences and number of pulses have been used in order to optimize the LIPSS morphology. Ripples period and depth can be tuned by laser parameters. In particular, the high optical absorption of P3HT at 532 nm enables the formation of well-ordered nanostructures with periodicities around 460 nm. Near edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopy reveal a good chemical stability of P3HT thin films during LIPSS formation. Conducting atomic force microscopy (C-AFM) performed on the LIPSS reveals a higher electrical conduction in the trenches than in the ridge regions. Resonance Raman spectroscopy and grazing incidence wide-angle X-ray scattering (GIWAXS) indicate a loss of crystallinity of P3HT thin films during LIPSS formation, suggesting melting of the outer polymer surface. This effect produces ridges with molecular order lower than that of the original thin film. As a consequence of this transformation, the electrical conduction in the ridges becomes lower than that in the trenches.The authors gratefully acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness (MINECO) through Projects MAT 2011-23455, MAT 2012-33517 and CTQ 2013-43086-P. A.R.-R. and E.R. are indebted to MINECO for a FPI (BES-2013-062620) and Ramon y Cajal (RYC-2011-08069) contracts, respectively. We thank the Swiss Light Source for beamtime at PolLux, where the NEXAFS experiments were performed. We also thank the ESRF for beamtime at BM26 where in situ GISAXS and GIWAXS experiments were carried out. We thank B. Watts for assistance in using beamline PolLux and G. Portale and W. Bras for beamline support at BM26. P. Müller-Buschbaum and S. Guo are thanked for seminal comments at the beginning of this workPeer Reviewe

Mapping the structural order of laser-induced periodic surface structures in thin polymer films by microfocus beam grazing incidence small-angle x-ray scattering

In this work we present an accurate mapping of the structural order of laser-induced periodic surface structures (LIPSS) in spin-coated thin polymer films, via a microfocus beam grazing incidence small-angle X-ray scattering (μGISAXS) scan, GISAXS modeling, and atomic force microscopy imaging all along the scanned area. This combined study has allowed the evaluation of the effects on LIPSS formation due to nonhomogeneous spatial distribution of the laser pulse energy, mapping with micrometric resolution the evolution of the period and degree of structural order of LIPSS across the laser beam diameter in a direction perpendicular to the polarization vector. The experiments presented go one step further toward controlling nanostructure formation in LIPSS through a deep understanding of the parameters that influence this process

Mapping the structural order of laser-induced periodic surface structures in thin polymer films by microfocus beam grazing incidence small-angle x-ray scattering

8 pags,; 7 figs.; 1 tab.© 2015 American Chemical Society. In this work we present an accurate mapping of the structural order of laser-induced periodic surface structures (LIPSS) in spin-coated thin polymer films, via a microfocus beam grazing incidence small-angle X-ray scattering (¿GISAXS) scan, GISAXS modeling, and atomic force microscopy imaging all along the scanned area. This combined study has allowed the evaluation of the effects on LIPSS formation due to nonhomogeneous spatial distribution of the laser pulse energy, mapping with micrometric resolution the evolution of the period and degree of structural order of LIPSS across the laser beam diameter in a direction perpendicular to the polarization vector. The experiments presented go one step further toward controlling nanostructure formation in LIPSS through a deep understanding of the parameters that influence this process.The authors acknowledge financial support from MINECO (grants MAT2009-07789, CTQ2010-15680, CTQ2013-43086, MAT2011-23455 and MAT2012-33517, FPI BES-2010- 030074 and Ramón y Cajal contract RYC-2011-08069). The assistance of S. Roth at PO3 (PETRA III) is greatly acknowledged.Peer Reviewe

Mapping the Structural Order of Laser Induced Periodic Surface Structures in Thin Polymer Films by Microfocus Beam

SRPS6, Madrid (Spain), 7-10 September 2015; http://srps6.com/scientific-program/program/Peer Reviewe

Laser-induced periodic surface structures on P3HT and on its photovoltaic blend with PC71BM

8 págs.; 9 figs.We describe the conditions for optimal formation of laser-induced periodic surface structures (LIPSS) over poly(3-hexylthiophene) (P3HT) spin-coated films. Optimal LIPSS on P3HT are observed within a particular range of thicknesses and laser fluences. These conditions can be translated to the photovoltaic blend formed by the 1:1 mixture of P3HT and [6,6]-phenyl C-butyric acid methyl ester (PCBM) when deposited on an indium tin oxide (ITO) electrode coated with (poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). Solar cells formed by using either a bilayer of P3HT structured by LIPSS covered by PCBM or a bulk heterojunction with a P3HT:PCBM blend structured by LIPSS exhibit generation of electrical photocurrent under light illumination. These results suggest that LIPSS could be a compatible technology with organic photovoltaic devices. Copyright © 2016 American Chemical SocietyThis work has been supported by Spanish Ministry of Economy under the projects CTQ 2013-43086-P, MAT2014-59187-R, and MAT2015-66443-C02-1-R. J.C. acknowledges the China Scholarship Council for funding her research (File NO. 201207040083). E.R. and A.R-R thank MINECO for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069) and FPI (BES-2013-062620) contracts, respectively. P.M.-B. and D.M.G. acknowledge financial support by TUM.solar in the frame of the Bavarian Collaborative Research Project “Solar technologies go Hybrid” (SolTec), by the GreenTech Initiative (Interface Science for PhotovoltaicsISPV) of the EuroTech Universities and by the Nanosystems Initiative Munich (NIM). We thank Daniel Hermida and Wim Bras for outstanding support during beamtime in DUBBLE at ESRF. Fruitful comments of A. Urbina are gratefully acknowledged.Peer Reviewe

Laser induced periodic surface structures (LIPSS) on semiconducting polymers: poly(3-alkylthiophene)

Organized by Nanolito will be held in Zaragoza from 28th to 30th October, 2014 ; http://unizar.es/nanolito/nanolito2014/index.htmlPeer Reviewe

Grazing Incidence Small Angle X-Ray Scattering (GISAXS) as a tool for characterization and optimization of polymer nanostructures

Peer Reviewe

In situ monitoring of laser induced periodic surface structures on conjugated polymers of interest in organic photovoltaics

E-MRS Spring Meeting (European Materials Research Society); Lille (France); May 2 to 6 2016; http://www.european-mrs.com/2016-spring-symposium-cc-european-materials-research-societyFormation of laser induced periodic surface structures (LIPSS) has been observed on polymers upon irradiation with a linearly polarized laser beam, at wavelengths efficiently absorbed and within a narrow fluence range below the ablation threshold. LIPSS are the result of the interference between the incoming and the surface-scattered waves together with a feedback mechanism. The use of grazing incidence X-ray scattering techniques with synchrotron radiation can be very useful for LIPSS analysis as they can provide kinetic information in the millisecond range and structural information statistically averaged over a large area. We report on the formation of LIPSS on conjugated polymers of interest in organic photovoltaics upon irradiation with the second and fourth harmonics of a Nd:YAG laser (532 and 266 nm) followed online by synchrotron Grazing Incidence X-ray Scattering at small (GISAXS) and wide (GIWAXS) angles. In situ measurements were performed at the DUBBLE beamline of the European Synchrotron Radiation Facility in order to study the evolution of the structural features online upon repetitive irradiation and to obtain information about the mechanisms involved in LIPSS formation. The number of pulses needed for the onset of LIPSS formation and for achieving the optimal order of the structures varies for the different polymers and irradiation conditions. The real time monitoring allows online optimization of both laser fluence and repetition rate for LIPSS formation