Effect of oxygen gas on polycarbonate surface in keV energy Ar + ion irradiation
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Effect of oxygen gas on polycarbonate surface in keV energy Ar1 ion irradiation Jun-Sik Cho, Won-Kook Choi, Hyung-Jin Jung, and Seok-Keun Koh Division of Ceramics, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea
Ki Hyun Yoon Department of Ceramic Engineering, Yonsei University, Seoul 120-701, Korea (Received 3 September 1995; accepted 4 December 1995)
Ar1 ion irradiation on a polycarbonate (PC) surface was carried out in an oxygen environment in order to investigate the effects of surface chemical reaction, surface morphology, and surface energy on wettability of PC. Doses of Ar1 ion were changed from 5 3 1014 to 5 3 1016 at 1 keV ion beam energy by a broad ion beam source. Contact angle of PC was not reduced much by Ar1 ion irradiation without flowing oxygen gas, but decreased significantly as Ar1 ion was irradiated with flowing 4 sccm (mlymin) oxygen gas and showed a minimum of 12± to water and 5± to formamide. A newly formed polar group was observed on the modified PC surface by Ar1 ion irradiation with flowing oxygen gas, and it increased the PC surface energy. On the basis of x-ray photoelectron spectroscopy analysis, the formed polar group was identified as a hydrophilic C°°O bond (carbonyl group). In atomic force microscopy ˚ to (AFM) study, the root mean square of surface roughness was changed from 14 A ˚ by Ar1 ion irradiation without flowing oxygen gas and 26 –30 A ˚ by Ar1 ion 22–27 A irradiation with flowing 4 sccm oxygen gas. It was found that wettability of the modified PC surface was not greatly dependent on the surface morphology, but on an amount of hydrophilic group formed on the surface in the ion beam process.
I. INTRODUCTION
Surface characteristics of polymers determine their interfacial properties and technological applications such as adhesion to metal, wettability, solubility, etc. Previously many methods containing plasma, corona, arc discharge, dc or rf sputter etching, g-ray, ultraviolet light, ion beam, etc.1–8 have been executed to modify the surface properties of polymers. Changes in the chemical and physical properties of polymer at the surface region may be easily derived by chemical and/or structural modifications which can be achieved by variations of chemical functionality, surface texture, and wettability of polymers through the above-mentioned various surface treatment techniques. Many extensive studies have been reported about improving wettability of polymer by using plasma discharge, ion beam modification with a few MeV and 100s keV energy,9–12 and they have tried to explain relations among the changes in different physical/chemical characteristics of the polymer surface in view of surface morphology or interaction between the charged particle and the bulk of polymer. According to Fakes et al.,13 it was reported that the mean contact angle of water to modified PMMA (polymethylmethacrylate) surface by using O2 plasma discharge decreased from 70.7± to 49.5±, and this drop J. Mater. Res.,
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