Applied Surface Science 257 (2011) 6021–6025 Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Angle dependent laser nanopatterning of poly(ethylene terephthalate) surfaces P. Slepiˇ cka a,∗ , A. Chaloupka a , P. Sajdl b , J. Heitz c , V. Hnatowicz d , V. ˇ Svorˇ cík a a Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague, Czech Republic b Department of Power Engineering, Institute of Chemical Technology, 166 28 Prague, Czech Republic c Institute of Applied Physics, Johannes Kepler University, 4040 Linz, Austria d Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Rez, Czech Republic article info Article history: Received 17 October 2010 Received in revised form 20 December 2010 Accepted 21 January 2011 Available online 1 February 2011 Keywords: Polyethyleneterephtalate Excimer laser Ripples Gold Sputtering Morphology abstract Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene tereph- thalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157 nm laser. In a certain range of irradiation parameters, the irradiation resulted in the forma- tion of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentra- tion in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Surface morphology and chemical properties play impor- tant role in the interaction living cells or metals with polymer surface [1]. Laser treatment is essentially a dry process that makes it possible to alter the surface properties of the materi- als while maintaining desirable intrinsic bulk properties. Excimer laser treatment has found wide spectrum of applications in biomedicine and biotechnology, micro-electronics where it may improve surface properties of polymers or facilitate metalliza- tion process. Laser irradiation may lead to improved adhesion at metal/polymer interface [2]. It was reported that the treatment of poly(ethylene terephthalate) (PET) by excimer laser before metal- lization improved the Al/PET adhesion significantly [3]. Irradiation with 157 nm laser was applied to ITO films to drive strong linear optical interactions and to improve etching precision and surface morphology for patterning transparent electrodes together with micro-channels [4]. Several studies have shown that the illumination of polymers by polarized UV-laser beam induces self-organized ripple structure ∗ Corresponding author. Tel.: +420 220 445 159. E-mail address: petr.slepicka@vscht.cz (P. Slepiˇ cka). formation within a narrow fluence range well below the ablation threshold [5–9]. These periodic or ripple-like surface structures in the range of microns and sub-microns were generated on poly- mer surface without using a photo mask. The period of the ripples depends on the laser wavelength and on the angle of incidence of the laser beam. Ripple direction is related to the direction of the laser light polarization [10]. The spacing of the structures can be described by the relation:  =  n - sin  (1) where  is the lateral periodicity of the structures,  is the wave- length of the excitation laser light, n is the effective refractive index of the material and  is the angle of incidence of the laser beam. It is known that the interference between the incoming and the surface scattered waves plays an important role in the structure for- mation [11]. The interference causes an inhomogeneous intensity distribution which, together with a feedback mechanism, results in the enhancement of the modulation depth [7]. However, the whole mechanism is more complex and different processes have been reported as responsible for ripple formation [5,7,12], such as thermal and non-thermal scissoring of polymer chains, amorphiza- tion of crystalline domains, local surface melting, photooxidation and material transport. 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.01.107