Structural studies of argon-sputtered amorphous carbon films by means of extended x-ray-absorption fine structure
The temperature-dependent microscopic structure of plasma-deposited a-C:H and magnetron-sputtered a-C films, in situ sputter cleaned by argon bombardment, has been investigated by near-edge (NEXAFS) and extended (EXAFS) x-ray-absorption fine-structure studies. We find that the microscopic structure of the two films becomes indistinguishable after sputtering with a loss of hydrogen for the a-C:H sample. The structure of the sputtered films at 30 /sup 0/C is characterized by a first-neighbor C-C bond length of 1.445(10) A. Upon annealing the bond length approaches that of graphite (1.421 A) with a value of 1.427(10) A at 1050 /sup 0/C, the highest annealing temperature used. Analysis of the EXAFS amplitude of the first-neighbor shell leads to a two-phase structural model consisting of a ''graphitelike'' network and a statically and dynamically disordered ''random matrix.'' The fraction of carbon atoms in the ''graphitelike'' network increases from 60(6)% at 30/sup 0/C to 92(9)% at 1050/sup 0/C. Analysis of the higher-neighbor-shell EXAFS signals leads to a model for the ''graphitelike'' regions, consisting of a network of conjugated odd- and even-membered rings, without long-range order. In contrast, the ''random matrix'' is suggested to be a mostly chainlike network of double and single bonds. Our results suggest that the ''graphitelike'' matrix is a precursor state for crystallization.
- Research Organization:
- IBM Research Division, Almaden Research Center, San Jose, California 95120-6099
- OSTI ID:
- 6932361
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:11; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603* -- Materials-- Properties
ABSORPTION SPECTRA
AMORPHOUS STATE
ANNEALING
BOND LENGTHS
CARBON
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DIMENSIONS
ELEMENTAL MINERALS
ELEMENTS
FILMS
FINE STRUCTURE
GRAPHITE
HEAT TREATMENTS
HYDROGENATION
LENGTH
MICROSTRUCTURE
MINERALS
NONMETALS
PLASMA
SPECTRA
SPUTTERING
STRUCTURAL MODELS
TEMPERATURE DEPENDENCE
X-RAY SPECTRA