APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013;
Baltimore, Maryland
Session B5: Focus Session: Van der Waals Bonding in Advanced Materials - Surfaces, Growth, and Friction
11:15 AM–2:03 PM,
Monday, March 18, 2013
Room: 301
Sponsoring
Unit:
DMP
Chair: Jacqueline Krim, North Carolina State University
Abstract ID: BAPS.2013.MAR.B5.1
Abstract: B5.00001 : Exploiting London dispersion forces in nonequilibrium growth of surface-based nanostructures*
11:15 AM–11:51 AM
Preview Abstract
Abstract
Author:
Zhenyu Zhang
(Univ of Science \& Technology of China \& Univ of Texas at Austin)
London dispersion force$^{\, }$describes the weak interaction between
transient dipoles or multipoles associated with different parts of matter,
and accounts for a major part of the attractive van der Waals (vdW) force.
It is ubiquitous in nature, yet its importance in various physical and
chemical processes just starts to be increasingly recognized. Such advances
through definitive quantitative studies are largely enabled by the
availability of more accurate descriptions of the weak interactions
associated with long-range electron correlation effects within
first-principles approaches.
The present talk contains two parts, both obtained within the vdW-DF scheme
on the theory side. In the first part, we critically assess the binding
strengths of different classes of adatoms on ultrathin metal films of
varying thicknesses. For inert gas atoms such as Xe, the London dispersion
force is found to drastically enhance their adsorption, but the overall
binding behavior depends only weakly on the film thickness. In contrast, for
atoms with unpaired valence electrons such as H or O, the overall binding is
much stronger, and also depends more sensitively on the film thickness, but
with a much weaker and (in some cases) repulsive vdW contribution. These
results have important implications in our developing a better understanding
of atomic and molecular adsorption on different metal substrates. In the
second part, we demonstrate unambiguously the decisive role of London
dispersion force in non-equilibrium growth of ordered nanostructures on
metal substrates using aromatic source molecules. Our multi-scale modeling
integrating first-principles calculations with kinetic rate equation
analysis shows that a drastic reduction in the growth temperature, from
1000$^{\circ}$C to (250-300)$^{\circ}$C, can be achieved in graphene
growth on Cu(111) when the typical carbon source of methane is replaced by
benzene or $p$-Terphenyl. The enhanced London dispersion forces effectively
prevent easy desorption of the adsorbed molecules, facilitating their
dehydrogenation, and promoting subsequent graphene growth at much lower
temperatures. These strong predictions are further validated quantitatively
in our experimental tests. We also demonstrate that the general trends
established above are broadly applicable in graphene growth using other
aromatic carbon sources.
*Work done in collaboration with Jin-Ho Choi, Ping Cui, Guo Li, Wenguang Zhu on the theory side, and Zhancheng Li, Xiaodong Fan, and Changgan Zeng on the experimental side; supported in part by NSF and MOST of China, USNSF, and USDOE.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.B5.1