Deposition of Highly Ordered CF 2 -Rich Films Using Continuous Wave and Pulsed Hexafluoropropylene Oxide Plasmas Carmen I. Butoi, Neil M. Mackie, Lara J. Gamble, † David G. Castner, † Jeffrey Barnd, Anne M. Miller, and Ellen R. Fisher* Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872 Received March 20, 2000. Revised Manuscript Received May 15, 2000 The structure and composition of fluorocarbon materials deposited in pulsed and continuous wave (CW) hexafluoropropylene oxide (HFPO) plasmas were investigated. Results indicate substantial dependence on substrate position relative to the rf coil. When the substrate was placed 8 cm downstream from the rf coil (25 W CW), highly amorphous, cross-linked films were obtained. In contrast, materials deposited 28 cm downstream from the rf coil contained less cross-linked moieties and a higher degree of order. Angle-resolved X-ray photoelectron spectroscopy (XPS) C 1s analysis showed that the 28 cm materials contain up to ∼80% CF 2 and CF 3 surface-enriched layers. Static secondary ion mass spectroscopy (SIMS) data revealed that these fluorocarbon materials are composed of long CF 2 chains. Near edge X-ray absorption fine structure (NEXAFS) analysis showed that the CF 2 chains were oriented perpendicular to the substrate surface for the films deposited at 28 cm downstream, while the films obtained 8 cm downstream do not exhibit any particular orientation. The compositions of materials deposited in pulsed HFPO systems have rf power and distance dependencies similar to those observed in the CW plasmas. I. Introduction Over the past 20 years, pulsed rf plasmas have been successfully employed in plasma polymerization of a variety of monomers. 1,2,3 With pulsed plasma polymer- ization, high retention of the monomer functional group in the resulting polymeric film can be achieved. 4 In addition, pulsed plasmas provide access to lower con- tinuous wave (CW) equivalent powers because the rf power is on for only a portion of the cycle time. Use of pulsed sources reduces trapped radicals in the film, lowers deposition surface temperatures, decreases high- energy ion bombardment and UV flux to the surface, and provides greater control over the resulting film chemistry. 5 In contrast, films deposited from CW plas- mas are often amorphous polymeric materials with little resemblance to the original monomer. 6,7 This is partially because CW plasmas can significantly fragment and scramble monomer functional groups through complex recombination and addition reactions. 8 However, ma- terials generated at very low CW powers have been shown to retain some monomer functionalities. 9 Alter- natively, we have previously reported the use of pulsed rf plasmas to produce a variety of hydrogenated and fluorinated organic films with a high degree of control- lability over film composition. 4 Alternatives to pulsed plasma film deposition are provided by plasma-enhanced chemical vapor deposition (PECVD) using downstream and remote CW plasmas, which also decrease energetic species bombardment of the deposited material. Again, this eliminates undesired effects usually associated with the use of CW plasmas and can produce films with unique properties. 10,11,12 Fluorocarbon materials deposited in this manner have been shown to possess low dielectric constants 13 and increased biocompatibility. 14,15 O’Kane and Rice re- ported pronounced composition differences between films generated at different distances from the rf glow † Department of Bioengineering and Chemical Engineering, Uni- versity of Washington, Box 1750, Seattle, WA 98195-1750. (1) Yasuda, H.; Hsu, T. J. Polym. Sci., Polym. Chem. Ed. 1977, 15, 81-87. (2) Rinsch, C. L.; Chen, X.; Panchalingam, V.; Eberhart, R. C.; Wang, J. H.; Timmons, R. B. Langmuir 1996, 12, 2995. (3) Savage, C. R.; Timmons, R. B.; Lin, J. W. In Structure-Property Relations in Polymers; Advances in Chemistry Series 236; American Chemical Society: Washington, DC, 1993; p 745. (4) Mackie, N. M.; Castner, D. G.; Fisher, E. R. Langmuir 1998, 14, 1227-1235. Mackie, N. 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