In this work we evaluate the potential of grazing incidence X-ray scattering techniques in the investigation of laserinduced periodic surface structures (LIPSSs) in a series of strongly absorbing model spin-coated polymer films which are amorphous, such as poly(ethylene terephthalate), poly(trimethylene terephthalate), and poly(carbonate bisphenol A), and in a weaker absorbing polymer, such as semicrystalline poly(vinylidene fluoride), over a narrow range of fluences. Irradiation was performed with pulses of 6 ns at 266 nm, and LIPSSs with period lengths similar to the laser wavelength and parallel to the laser polarization direction are formed by devitrification of the film surface at temperatures above the characteristic glass transition temperature of the polymers. No crystallization of the surface is induced by laser irradiation, and crystallinity of the material prevents LIPSS formation. The structural information obtained by both atomic force microscopy and grazing incidence small-angle X-ray scattering (GISAXS) correlates satisfactorily. Comparison of experimental and simulated GISAXS patterns suggests that LIPSSs can be well described considering a quasi-onedimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice.

No abstract

The generation of nanostructured polymer films has been a challenge during the last decades. Surface nanostructuring based on the imprinting of nanoscale patterns on a homogeneous surface or on the deposition of nanostructures on the surface serves advantageously for nanofabrication of functional polymer materials. Advanced nanolithography typically requires multiple-steps procedures involving clean-room facilities, high vacuum or complex mask fabrication. Alternatively, laser-based methods enable high spatial resolution patterning of soft polymeric matter and afford the sought versatility and reliability without the need of stringent ambient conditions. In particular, the technique of laser induced periodic surface structures (LIPSS) has been successfully applied to nanostructuring of polymer films using a polarized laser source at several laser wavelengths and pulse durations. In this paper the formation of LIPSS on polymer films will be described. In particular, the possibilities of tuning the period and shape of the structures will be discussed since the control of the characteristics of the superficial structures can be crucial in order to match the requirements of a particular application.Additionally, an overview about the main and potential applications of LIPSS in polymer films is provided. In particular, the use of rippled polymer films as substrates for cell culture/alignment, surface enhanced Raman scattering sensors, or applications in photovoltaics will be reviewed.

Here we present a precise morphological description of laser-induced periodic surface structures (LIPSS) nanofabricated on spin-coated poly(trimethylene terephthalate) (PTT) films by irradiation with 266 nm, 6 ns laser pulses and by using a broad range of fluences and number of pulses. By accomplishing real and reciprocal space measurements by means of atomic force microscopy and grazing incidence wide- and small-angle X-ray scattering respectively on LIPSS samples, the range of optimum structural order has been established. For a given fluence, an increase in the number of pulses tends to improve LIPSS in PTT. However, as the pulse doses increase above a certain limit, a distortion of the structures is observed and a droplet-like morphology appears. It is proposed that this effect could be related to a plausible decrease of the molecular weight of PTT due to laser-induced chain photo-oxidation by irradiation with a high number of pulses. A concurrent decrease in viscosity enables destabilization of LIPSS by the formation of droplets in a process similar to surface-limited dewetting.