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Stress balance in nano-patterned N/Cu(001) surfaces | S. Hong
; T. S. Rahman
; E. Z. Ciftlikli
; B. J. Hinch
; | Date: |
1 Sep 2011 | Abstract: | We employ helium atom scattering (HAS) and density functional theory (DFT)
based on the ultrasoft pseudopotential scheme and the plane-wave basis set to
investigate the strain and stress balance in nano-patterned N/Cu(001) surfaces.
HAS shows that, with increasing N coverage (and decreasing stripe widths), the
stress-relief-driven lateral expansion of the averaged lattice parameter within
finite-sized N-containing patches reduces from 3.5% to 1.8% and that, beyond a
critical exposure, the lateral expansion of the patches increases again
slightly, to 2.4%. The latter implies that in this higher coverage range the
compressive stress is partially relieved via another mechanism, which turns out
to be nucleation of Cu-vacancy trenches. In full agreement with the above and
previous experimental observations, DFT calculations show that an optimized
N-induced c(2 imes2) structure has a net surface stress level of 4.2 N/m and
such stress is effectively relieved when stripes of clean Cu(001) form along
the <100> direction or when trench-like steps of Cu atoms form along the <110>
direction. Additionally, the calculations demonstrate that (contrary to earlier
suggestions) rumpling displacements within the outermost Cu layer do not act to
relieve the compressive surface stress levels and that, while clock-like
displacements could relieve stress levels, such displacements are energetically
unstable. | Source: | arXiv, 1109.0190 | Services: | Forum | Review | PDF | Favorites |
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