Gold nano-wires and nano-layers at laser-induced nano-ripples on PET J. Siegel a , P. Slepic ˇka a , J. Heitz b , Z. Kolska ´ c , P. Sajdl d , V. S ˇ vorc ˇı ´k a, * a Department of Solid State Engineering, Institute of Chemical Technology, Technicka 5, 166 28 Prague, Czech Republic b Institute of Applied Physics, Johannes Kepler University, 4040 Linz, Austria c Department of Chemistry, J.E. Purkyneˇ University, Usti nad Labem, Czech Republic d Department of Power Engineering, Institute of Chemical Technology, 166 28 Prague, Czech Republic 1. Introduction Surface modification and structure formation at polymers are an important application of UV-radiation. Polymer surfaces can be modified, e.g. by deep UV-irradiation of an excimer lamp [1,2], light emitted by an atmospheric pressure plasma source [3,4] or by excimer laser beams [5–8]. Laser-induced modification can lead to the coloration of polymers [9]. Laser-pattern is employed for the production of polymeric semiconductors and insulators on flexible polymeric substrates field effect transistors (PFETs) [10]. By defining planar nanostructures on polymer surfaces, it is possible to improve the parameters in polymer electronic memories [11]. Laser surface texturing is used also for the design and manufacturing of biomedical surfaces [12]. Surface modification of PET with excimer laser irradiation can influence the physical and biological proper- ties used for medical devices [13]. Periodic surface structures can regulate the cellular adhesion behaviors on PET substrate [14]. Also excimer laser modification of polymer surfaces without pattern formation can influence adhesion, proliferation, morphology, viability or migration of cells seeded at such modified samples [15–18]. Surface exposure of polymer to plasma [19] or laser beam [20] can also affect the adhesion of consecutively deposited metal layer. The influence on adhesion of surface modification can be due to the change of surface morphology or chemistry and creation of oxygen atoms containing groups on polymer’s surface [19–22]. Nanos- tructured materials and metal nano-layers are being extensively studied in the field of microelectronics, such as sensors, actuators, photovoltaics, and polymeric displays [23–25]. Several studies have shown that the illumination of polymers by polarized UV laser beam induces self-organized ripple structure formation within a narrow fluence range well below the ablation threshold [26–30]. The properties of these periodic structures have been frequently studied since the first report about them [31]. The smallest features on polymers reported so far produced by our group by 157 nm F 2 laser irradiation of polyethyleneterephthalate [32]. The period of the ripples depends on the laser wavelength and on the angle of incidence of the radiation, and their direction is related to the direction of the laser beam polarization [33]. The spacing of the structures can be described by the relation: L ¼ l ðn  sin uÞ (1) Applied Surface Science 256 (2010) 2205–2209 ARTICLE INFO Article history: Received 4 September 2009 Received in revised form 18 September 2009 Accepted 18 September 2009 Available online 30 September 2009 Keywords: KrF and F 2 laser Polyethyleneterephthalate Ripples Au sputtering Nano-wires Nano-layers ABSTRACT Gold nano-layers were deposited onto laser irradiated polyethyleneterephthalate (PET) surfaces. For irradiation, we used the linearly polarized light of a pulsed 248 nm KrF and 157 nm F 2 laser, respectively. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns with a lateral periodicity in the order of the wavelength of the laser light and with a corrugation height of several 10 nm. The deposited layers were then prepared by sputtering. The layers were analyzed by atomic force microscopy (AFM), focused ion beam (FIB) cuts, scanning electron microscopy (SEM), and angular resolved X-ray induced photoelectron spectroscopy (ARXPS). Gold sputtering on KrF laser irradiated PET led to the formation of separated ‘‘nano-wires’’ at the ridges of the nano-patterns and not to a continuous metal layer, as we obtained in case of gold sputtering onto F 2 irradiated PET. The results of the XPS analysis indicated, that the KrF irradiation caused degradation on the ridge of the ripples, whereas no noticeable degradation occurred for F 2 laser treatment. We attribute the different growth mechanisms of the deposited gold layers mainly to the difference in surface chemical composition of laser irradiated PET with the two different lasers employed. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: Vaclav.svorcik@vscht.cz (V. S ˇ vorc ˇı ´k). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.09.074