CNMS User Research
Charge Order Fluctuations in One-Dimensional Silicides
Zeng1, P. R.C. Kent2, Tae-Hwan Kim2,
and Hanno H. Weitering1,3
1Department of Physics and Astronomy, The University of Tennessee,
2Center for Nanophase Materials Sciences, Oak Ridge National
3Materials Science and Technology Division, Oak Ridge National
Exceptionally long and uniform YSi2 nanowires have been fabricated
via self-assembly of yttrium atoms on Si(001). The wire widths are
quantized in odd multiples of the Si substrate lattice constant.
An electronic phase transition from a metal to a charge-ordered insulator
has been revealed on the nanowires. The thinnest wires, 3asi-wide,
represent one of the closest realizations of the isolated Peierls
chain, exhibiting van Hove type singularities in the one-dimensional
density of states and charge order fluctuations below 150 K. The
structure of the wire was determined through a detailed comparison
of scanning tunneling microscopy data and first-principles calculations.
Quantized width variations along the thinnest wires produce built-in
Schottky junctions whose electronic properties are governed by the
finite-size and temperature-scaling of the charge ordering correlation.
Our observations provide clear evidence for short-range charge order
in one-dimensional chains that are electronically decoupled from
neighboring chains and from the semiconducting substrate. They capture
a rare glimpse in real space into the destruction of one-dimensional
charge order at higher temperature. Both charge ordered insulating
phase and metallic phase have been manifested on individual nanowires
as a metallic I-V spectrum on the 5asi-wide side and an insulating
one on the 3asi-wide side. This one-dimensional Schottky-type barrier
device can be controlled by varying the temperature around the charge
ordering transition. These remarkable nanowires with built-in junctions
illustrate how the finite-size- and temperature-scaling behavior
of a collective phenomenon might one-day be exploited in novel nano-architectures.
“Charge Order Fluctuations in One-Dimensional Silicides,” Changgan
Zeng, P. R.C. Kent, Tae-Hwan Kim, An-Ping Li, and Hanno H. Weitering,
Nature Materials 7, 539 (2008).
The research was sponsored by the National Human Genome Research Institute,
National Institutes of Health Grant R01HG002647 (CZ), NSF (CZ) and
by U. S. Department of Energy through the Center for Nanophase Materials
Sciences, which is sponsored by the Division of Scientific User Facilities,
and through computational resources from the National Energy Research
Scientific Computing Center and from the National Center for Computational
Sciences at Oak Ridge National Laboratory, which are supported by
the Office of Science.
topography of YSi2 nanowires. a,
Large scale STM image of self-assembled YSi2 nanowires
on Si(001). The scale bar corresponds to 50 nm. b,
High resolution filled-state STM image scanned at RT. c,
Simulated filled-state STM image on a 3aSi-wide
YSi2 nanowire adopting the structure model as
shown in Fig. b. d, Cross-sectional line
profile on a 3aSi-wide YSi2 nanowire.
ordering in YSi2 nanowires.
a, STM image scanned at 40 K. The scale bar
represents 5 nm. b and c,
Registry aligned dual bias STM images scanned simultaneously
at 40 K with a sample bias of -0.8 V and 0.8 V, respectively. d,
Line profiles along lines ‘a’ and ‘b’ in b and c,
respectively. The curves are shifted vertically for clarity. e,
Statistical distributions of the spacings between neighboring
charge density maxima in filled-state STM images for different
temperatures. f and g, STM
images of 5aSi-wide and 7aSi-wide YSi2 nanowires
at 40 K. The image widths in f and g are
both 14 nm. There is no charge ordering.