Title: Periodic nanostructure induced on PEN surface by KrF laser irradiation

Authors: P. Slepička; O. Neděla; N. Slepičková Kasálková; P. Sajdl; V. Švorčík

Addresses: Department of Solid State Engineering, University of Chemistry and Technology, Technicka 3, 166 28 Prague, Czech Republic ' Department of Solid State Engineering, University of Chemistry and Technology, Technicka 3, 166 28 Prague, Czech Republic ' Department of Solid State Engineering, University of Chemistry and Technology, Technicka 3, 166 28 Prague, Czech Republic ' Department of Power Engineering, University of Chemistry and Technology, Technicka 3, 166 28 Prague, Czech Republic ' Department of Solid State Engineering, University of Chemistry and Technology, Technicka 3, 166 28 Prague, Czech Republic

Abstract: There are several kinds of periodic surface structures, ranging from dots to ripples. The most common pattern is a ripple-like structure, where the direction of the ripples is parallel with the main polarisation of the laser beam. The distance between individual ripples (their period) depends on several factors, namely: the chemical structure of the polymer, wavelength of the laser irradiation and the angle of laser beam incidence. Oriented polyethylene naphthalate (PEN) foils with a thickness of 50 μm were used. The samples were irradiated with a KrF laser under laser beam incidence 0-45° to the laser beam. Selected polymer samples were also exposed by irradiation through a contact mask. Surface roughness and the dimensions of the ripple-like structures were measured by atomic force microscopy in tapping mode. The concentration of the elements on the surface was obtained from Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS) spectra measured by X-ray Photoelectron Spectroscopy (XPS) spectrometer. The surface morphology and dimensions of prepared structures were evaluated and compared with those prepared on pristine samples without mask. The transition between the irradiated surface under the slits and the shielded surface in between the slits was evaluated. The optimal input parameters for nanopattern with high periodicity were determined. The shape and the surface roughness of the ripple pattern depend strongly on the angle of incidence of the laser beam. The surface roughness and ripple width increase with the angle of laser beam incidence. Irradiation with laser leads to changes in chemical composition of the PEN surface layer. Even at initial phase of pattern formation a significant increase of carbonyl and carboxyl groups was detected.

Keywords: polyethylene naphthalate; PEN foils; excimer lasers; KrF laser irradiation; ripples; surface properties; surface chemistry; nanopatterns; nanotechnology; periodic nanostructures; surface roughness; angle of incidence; laser beam; carbonyl; carboxyl groups; ripple width.

DOI: 10.1504/IJNT.2017.082458

International Journal of Nanotechnology, 2017 Vol.14 No.1/2/3/4/5/6, pp.399 - 409

Published online: 21 Feb 2017 *

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