Applied Surface Science 59 I. 19921267-271 Nmth-HolJnnd surface science Surface reconstruction of UV-laser irradiated poly(ethylene terephthalate) by atomic force microscopy Lothar Wefers :~, Dierk Knittel ~, Dirk Bosbach b, Werner Rammensee ~' and Eekhard Schollmeyer ~ a Deul~ches TexOIforsc,~emgsz,.,ttttttu~ Nurd- West e.V., Frankenring 2. D-4150 iO, efeld. Gerc*x~ny Mineratogi3ch Fetrographisches Imtm~t der Uni~'ersirfft .'It KbYn. 7Jilpicl¢er Stra~se 49, 1)-5000 K6ln 1. German)" Received II Fehruary 1992; accepled for publication 9 March 1c)92 Alomic force microscopy (AFNt) i~ ulilized for the evaluation of change in the surface topography of highly absorbing palm, ethylene terephthalate)(PET)films after UV-laser treatrnenl wilh 248 nm. Three-dimensional data of the surf~,ce micmstruc- ture were taken from ,samples. Particularly low Ilue~ce lreatmem wi~h a few laser pulses was studied. A change in surface topography was ~ound in re,allan to the number of pulses app|ied. 1. ~ntroduction Exeimer laser irradiatior~ of polymers yields, above a certain fluence threshold, a removal of material in the form of an ablative photode¢om- position [].2]. Below this threshold a chemical modification occurs like oxidation and sputtering off CO and CO z fractions. This irradiation can aEso be used to 8enerate a modification of the surface topography. The normally smooth surface of a polymer film can be modified to a well oriented, structured surface, This increase in roughness has a great effect on the physical prop- erties of the specimen. Especially adhesion of particles, coating and wetting properties could be changed [3]. The evalu~,'ion of these structures on poly- meric fibres, once formed, due to further laser pulses has oeen studied by Kesting et al, and can be exola;,Led by the thermoplastic behaviour of the polymer [4]. The starting stage of the effect remains still uncertain. Several theories have been proposed for the origin ~,f UV-laser induced microstruc- tures. Bahners et al. [5] propose a synergetic modei relaling :.],e structure generation to ama- terial transport phenomenon driven cooperatively by tension fields and laser induced temperature fields. It follows, as with other synergetic phe- nomena, that for the formation of a microstruc- ture a minimum amount of energy is necessaw. Further information about the beginning of the structure due to low energy and few pulses is very impor{ant for a basic understanding. Atomic force microscopy is a powerful tool for highly sensitive evaluation of three-dimensional surface topographies. Quantitative measurements in the realms of atomic scale are possible. In this paper AFM measurements ,~f microstruetures on biaxialty oriented PET film are prcsea:ed, which were produced by up to five laser pulses and a fluence of ~ 34 ,nJ/cm 2. The measurements al- low reeon~lruction ~f the surface structu,e from untreated and treated samples, 2. Experimental Biaxia]ly oriented PET film (Hostaphan BN 180, Kalfc-Hocchst, thickrcss 180 p.m) was used lOT these tests. The film~ were irradiated using a KzF hscr (248 nm, FWHM: 23 ns) at various 0169.1332/qz/$()S,Bt © ]q92 - Elsevier Science Ft,blishers B.V. All righl.~ reserved