Tight-binding molecular-dynamics simulation of impurities in ultrananocrystalline diamond grain boundaries.

Journal Article · Tue Jan 15 04:00:00 EST 2002 · Phys. Rev. B

OSTI ID:949290

Zapol, P; Sternberg, M; Curtiss, L A; Frauenheim, T; Gruen, D M

Ultrananocrystalline diamond (UNCD) films grown from hydrogen-poor plasmas have grain sizes of 3-10 nm, resulting in a large number of grain boundaries. We repon on density-functional-based tight-binding molecular-dynamics calculations of high-energy high-angle twist (100) grain boundaries in diamond as a model for the UNCD grain boundaries. About one-half of the carbons in the grain boundary are threefold coordinated and are responsible for states introduced into the band gap. Simulations were also performed for N, Si, and H impurities in (100) twist grain boundaries where substitution energies, optimized geometries, and electronic structures were calculated. Substitution energies were found to be substantially lower for the grain boundaries compared to the bulk diamond crystal. Nitrogen increases the number of threefold-coordinated carbons while hydrogen saturates dangling bonds. The electronic structure of UNCD is characterized by a large number of states in the band gap attributed to the bonding disorder and impurities in the grain boundaries.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 949290
• Report Number(s): ANL/MSD/JA-39649
• Journal Information: Phys. Rev. B, Journal Name: Phys. Rev. B Journal Issue: 4 ; Jan. 15, 2002 Vol. 65; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

08 HYDROGEN
BONDING
DIAMONDS
ELECTRONIC STRUCTURE
GRAIN BOUNDARIES
GRAIN SIZE
HYDROGEN
IMPURITIES
NITROGEN
SIMULATION