XPS, XANES and ToF-SIMS Characterization of Reactively Magnetron-sputtered Carbon Nitride Films†

The existence of β-C 3 N 4 with hardness characteristics similar or better than diamond was predicted in 1990 by Liu and Cohen. Many studies have since been devoted to the synthesis of this compound. In the present work, carbon nitride films were deposited by various reactive magnetron sputtering processes of graphite targets in pure nitrogen and characterized by AES, XPS, x-ray adsorption near-edge structure (XANES) and static time-of-flight SIMS (ToF-SIMS). Various bonding states (single and double bond) are observed between carbon and nitrogen atoms and between carbon atoms but there is no evidence in the XANES results for either the presence of carbon-nitrogen triple bonds or a pyridine-like ring structure. Surface N/C ratios were estimated to be close to 0.3. Carbon K-edge XANES lineshapes, the C 1s plasmon-loss structure and the calculated density (2.2 g cm -3 ) indicate that the films are similar to diamond-like carbon without long-range ordering. The presence of C x N y fragments with 1 ≤ y < 4 and the low abundance of CH x and CH x N y fragments in ToF-SIMS spectra further confirm that the carbon atoms do not adopt a graphite or pyridine-like cyclic two-dimensional structure and that the films are not significantly hydrogenated. A three-phase solid solution model is proposed for the composition of the films: a 'free' carbon phase, an sp 3 -carbon-nitrided phase and an sp 2 -carbon-nitrided phase. The relative proportion of these phases is influenced by the deposition conditions. Enhanced plasma ionization reactive magnetron sputtering leads to higher density and to a higher fraction of the sp 3 carbon phase.

[1]  Jerome J. Cuomo,et al.  Reactive sputtering of carbon and carbide targets in nitrogen , 1979 .

[2]  P. H. Fang.  On the βC3N4 search , 1995 .

[3]  Gene H. Haertling,et al.  ELECTRO-OPTIC MEASUREMENTS OF THIN-FILM MATERIALS BY MEANS OF REFLECTION DIFFERENTIAL ELLIPSOMETRY , 1995 .

[4]  D. A. Shirley,et al.  X-ray photoemission studies of diamond, graphite, and glassy carbon valence bands , 1974 .

[5]  T. Page,et al.  Structural and mechanical properties of carbon nitride CNx (0.2⩽x⩽0.35) films , 1996 .

[6]  I. Gouzman,et al.  POSSIBILITY OF CARBON NITRIDE FORMATION BY LOW-ENERGY NITROGEN IMPLANTATION INTO GRAPHITE : IN SITU ELECTRON SPECTROSCOPY STUDIES , 1994 .

[7]  R. Zuhr,et al.  Formation of C–N thin films by ion beam deposition , 1995 .

[8]  D. Briggs,et al.  High resolution XPS of organic polymers , 1992 .

[9]  J. H. Scofield,et al.  Hartree-Slater subshell photoionization cross-sections at 1254 and 1487 eV , 1976 .

[10]  Liu,et al.  Structural properties and electronic structure of low-compressibility materials: beta -Si3N4 and hypothetical beta -C3N4. , 1990, Physical review. B, Condensed matter.

[11]  P. E. Mijnarends,et al.  Physical properties of a-C: N films produced by ion beam assisted deposition , 1994 .

[12]  Gwyn P. Williams,et al.  Characterization of metal/organic molecule and metal/polymer interfaces by NEXAFS spectroscopy , 1990 .

[13]  I. Tomov,et al.  Effect of thermal self‐defocusing of degenerate four wave mixing in absorbing media , 1994 .

[14]  W. Sproul,et al.  Thermal behavior of carbon nitride and TiN/NbN superlattice films , 1995 .

[15]  Jack H. Judy,et al.  Structure and bonding studies of the C: N thin films produced by rf sputtering method , 1990 .

[16]  Wu,et al.  Observation of crystalline C3N4. , 1994, Physical review. B, Condensed matter.

[17]  J. Delafond,et al.  Formation of the crystalline β-C3N4 phase by dual ion beam sputtering deposition , 1995 .

[18]  Boyd,et al.  Carbon nitride deposited using energetic species: A two-phase system. , 1994, Physical review letters.

[19]  A. Benninghoven,et al.  In situ ToF‐SIMS/XPS investigation of nitrogen plasma‐modified polystyrene surfaces , 1994 .

[20]  Mansour,et al.  Photoelectron-spectroscopy study of amorphous a-CNx:H. , 1993, Physical review. B, Condensed matter.

[21]  R. W. Hoffman,et al.  Structural analysis of hydrogenated diamond-like carbon films from electron energy loss spectroscopy , 1990 .

[22]  A. Bensaoula,et al.  Physical properties of thin carbon nitride films deposited by electron cyclotron resonance assisted vapor deposition , 1995 .

[23]  Dejun Li,et al.  Ionized magnetron sputter deposition of amorphous carbon nitride thin films , 1995 .

[24]  S. Yoshida,et al.  Preparation and structure of carbon film deposited by a mass‐separated C+ ion beam , 1984 .

[25]  C. E. Brion,et al.  K-shell excitation of CH4, NH3, H2O, CH3OH, CH3OCH3 and CH3NH2 by 2.5 keV electron impact , 1974 .

[26]  Heon Kang,et al.  Interactions of low energy reactive ions with surfaces. IV. Chemically bonded diamond‐like films from ion‐beam deposition , 1988 .

[27]  I. Gouzman,et al.  Irradiation effects induced by reactive and non‐reactive low energy ion irradiation of graphite: An electron spectroscopy study , 1994 .

[28]  M. L. Cohen,et al.  Predicting useful materials. , 1993, Science.