Near-Edge X-ray Absorption Fine Structure of Hard Carbon Film Formed by Gas Cluster Ion Beam Assisted Deposition
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Near-edge X-ray Absorption Fine Structure of Hard Carbon Film Formed by Gas Cluster Ion Beam Assisted Deposition Kazuhiro Kanda1, Yutaka Shimizugawa1, Yuichi Haruyama1, Isao Yamada1,3, Shinji Matsui1, Teruyuki Kitagawa2, Mititaka Terasawa2, Harushige Tsubakino2, Tatsuo Gejo4 and Masao Kamada4 1 Himeji Institute for Technology, Laboratory of Advanced Science and Technology for Industry, Kamigori, Hyogo 678-1205, Japan. 2 Himeji Institute for Technology, Faculty of Engineering, Himeji, Hyogo 671-2201, Japan. 3 Collaborative Research Center for Cluster Ion Beam Process Technology, Kyoto University, Sakyo, Kyoto 606-8501, Japan. 4 Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan. ABSTRACT The coordination of the carbon atoms in the diamond-like carbon (DLC) films formed by Ar gas cluster ion beam (GCIB) assisted deposition of fullerene was investigated using synchrotron radiation. Near-edge x-ray absorption fine structure (NEXAFS) spectra of the carbon K-edge of the DLC films formed by various methods were measured over the excitation energy range 275-320 eV, using synchrotron radiation. On the basis of the analysis of the peak corresponding the transition of the excitation electron from carbon 1s orbital to π* orbital, relative sp2 contents of various DLC films were determined. The DLC films formed by Ar GCIB assisted fullerene deposition were found to consist of a high sp3 hybridized carbon. INTRODUCTION DLC (Diamond-like carbon) films have been widely used for a number of applications in the last few years. The DLC films are characterized by a different sp2/sp3 ratio, which influences the mechanical and the electronic properties. DLC films have been dominantly formed by vapor phase methods [1,2], however their properties are not sufficient for the various devices in the next generation. Gas cluster ion beam (GCIB) assisted deposition using fullerene as a carbon source was proposed as a novel method in DLC synthesis [3]. In this method, energetic gas cluster ions deliver extremely high densities into very localized and shallow atomic level regions of a substrate surface. Because the impact point of a cluster ion on the instant attains conditions of high pressure and high temperature, the phase transition from sp2 to sp3 is enhanced even when the substrate is held at room temperature. The characterization of the DLC films produced by GCIB assisted deposition was studied by near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The carbon K-edge data show that NEXAFS spectroscopy is sensitive to the local structure around the absorber carbon atom. The resonance from 1s orbital to π orbitals in sp2 carbon and the resonance from 1s orbital to σ orbitals in sp2 and sp3 carbons present a distinguishable difference in energy and a simple identification of each contribution can be made. Thus a quantitative determination of the sp2/sp3 can be performed. Our data indicate that the GCIB assisted deposition is excellent method to form the hard DLC film and NEXAFS technique is useful for the characterizati
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