Structural stability of heat-treated CoN/CN soft X-ray multilayers fabricated by dual-facing-target sputtering |
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Authors: | HL Bai EY Jiang CD Wang RY Tian |
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Institution: | (1) Department of Applied Physics, Tianjin University, Tianjin 300072, China (Fax: +86-022/23358329, E-mail: yhzhou@tju.edu.cn), CN |
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Abstract: | 286 , 176 (1996)]. (1) The interdiffusion critical wavelengths were calculated as 2.00–2.04 nm at temperatures ranging from 473
to 523 K, which is equal to those of Co/C multilayers within the experimental error, indicating that the interdiffusion behaviours
in the CoN/CN multilayers are still decided by the thermodynamic properties of the Co-C system. (2) The effective interdiffusivities
and macroscopic diffusion coefficients are smaller. (3) The activation energy for diffusion is larger. The features imply
that it is possible to improve the thermal stability of Co/C multilayers by doping with N atoms.
The high-temperature annealing results imply that the destructive threshold of the CoN/CN multilayers is 100–200 °C higher
than that of Co/C multilayers. The small-angle X-ray diffraction of CoN/CN soft X-ray multilayers indicates that the period
expansion of the multilayers is only 4% at 400 °C, and the interface pattern still exists even if they were annealed at 700 °C.
The large-angle X-ray diffraction and transmission electron microscopy analysis reveal that the crystalline process is significantly
retarded if doped with N atoms, leading to a smaller grain size at higher annealing temperatures.
The significant improvement of the thermal stability can be interpreted with Raman spectroscopy and X-ray photoelectron spectroscopy
analysis. The Raman spectra give the evidence that the formation of the sp3 bonding in the CN sublayers can be suppressed effectively by doping with N atoms, and thus the period expansion resulting
from the changes in the density of CN layers can be decreased considerably. The X-ray photoelectron spectra give information
about existence of the strong covalent bonding between N atoms and the ionic bonding between Co and N atoms, which can slow
down the tendency of the structural relaxation. The interstitial N atoms decrease the mobility of Co atoms, and thus the fcc
Co and hcp Co coexist even though the annealing temperature is much higher than the phase transformation temperature of 420 °C,
leading to the suppression of the grain growth.
Received: 29 May 1997/Accepted: 8 September 1997 |
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Keywords: | PACS: 68 65+g 68 55 Ln 68 35 Fx 68 60 Dv |
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