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Title: Facet Stability in Oxygen-Induced Nanofaceting of Re(1231)

Abstract

The stability of the various facets in oxygen-induced faceting of Re(121) has been studied by low-energy electron diffraction, scanning tunneling microcopy, and synchrotron-based high-resolution X-ray photoemission spectroscopy. When Re(121) is annealed at 800-1200 K in oxygen (10-7 Torr), the surface becomes completely covered with nanometer-scale facets, and its morphology depends on the substrate temperature and oxygen exposure. Especially, the (111) facet competes with the (101) facet in determining the surface morphology, and the stability of each facet relies on oxygen coverage. Using density functional theory, the O-Re binding energies on the facets for various oxygen concentrations are calculated to explain how the oxygen coverage affects the anisotropy of surface free energy, which in turn determines the morphology of the faceted surface.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
960143
Report Number(s):
BNL-83129-2009-JA
TRN: US201016%%1287
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Nano; Journal Volume: 1; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; ANISOTROPY; ELECTRON DIFFRACTION; FREE ENERGY; FUNCTIONALS; MORPHOLOGY; OXYGEN; PHOTOEMISSION; SPECTROSCOPY; STABILITY; SUBSTRATES; TUNNELING; national synchrotron light source

Citation Formats

Wang,H., Chan, A., Chen, W., Kaghazchi, P., Jacob, T., and Madey, T.. Facet Stability in Oxygen-Induced Nanofaceting of Re(1231). United States: N. p., 2007. Web. doi:10.1021/nn700238r.
Wang,H., Chan, A., Chen, W., Kaghazchi, P., Jacob, T., & Madey, T.. Facet Stability in Oxygen-Induced Nanofaceting of Re(1231). United States. doi:10.1021/nn700238r.
Wang,H., Chan, A., Chen, W., Kaghazchi, P., Jacob, T., and Madey, T.. Mon . "Facet Stability in Oxygen-Induced Nanofaceting of Re(1231)". United States. doi:10.1021/nn700238r.
@article{osti_960143,
title = {Facet Stability in Oxygen-Induced Nanofaceting of Re(1231)},
author = {Wang,H. and Chan, A. and Chen, W. and Kaghazchi, P. and Jacob, T. and Madey, T.},
abstractNote = {The stability of the various facets in oxygen-induced faceting of Re(121) has been studied by low-energy electron diffraction, scanning tunneling microcopy, and synchrotron-based high-resolution X-ray photoemission spectroscopy. When Re(121) is annealed at 800-1200 K in oxygen (10-7 Torr), the surface becomes completely covered with nanometer-scale facets, and its morphology depends on the substrate temperature and oxygen exposure. Especially, the (111) facet competes with the (101) facet in determining the surface morphology, and the stability of each facet relies on oxygen coverage. Using density functional theory, the O-Re binding energies on the facets for various oxygen concentrations are calculated to explain how the oxygen coverage affects the anisotropy of surface free energy, which in turn determines the morphology of the faceted surface.},
doi = {10.1021/nn700238r},
journal = {ACS Nano},
number = 5,
volume = 1,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We have studied oxygen-induced faceting of the atomically rough Re(1231) surface by means of Auger electron spectroscopy, low energy electron diffraction, and scanning tunneling microscopy (STM). In contrast to previous faceting studies on other refractory metal surfaces, where simple morphologies of the facets were reported, we find a coverage-dependent morphological evolution of the facets ranging from long sawtooth ridges to complex structures exposing four different facets. The faceting occurs only when oxygen coverage ({theta}) exceeds 0.5 monolayer (ML) and the surface is annealed at {>=}700 K. At low oxygen coverage (0.5 ML{<=}{theta}<0.7 ML), the O/Re(1231) surface becomes partially faceted uponmore » annealing; further increasing of oxygen coverage (0.7 ML{<=}{theta}<0.9 ML) causes the surface to become completely faceted, forming long sawtooth ridges along the [2113] direction with typical dimensions of {approx}8 nm in width and >50 nm in length upon annealing at 1000 K. The size of the ridges grows with annealing temperature and annealing time, and the distance between the ridges is quite uniform. The two sides of each ridge have (0110) and (1121) orientations, and atomic-resolution STM images reveal that the edge of the ridge is atomically sharp. For 0.9 ML{<=}{theta}<1 ML, a third set of facets, identified as (1010), emerges and truncates the original ridges. With the surface fully covered by oxygen ({theta}=1 ML), a fourth facet (0111) also becomes prominent upon annealing. This morphological evolution is accompanied by a reduction of the average ridge length along [2113], indicating that the (1121) facet is metastable. Our work demonstrates that even in a simple adsorbate/substrate system, the adsorbate-induced modification of the anisotropy of surface free energy can induce a complex sequence of changes in the surface morphology. The faceted Re surfaces may be model systems to study structure sensitivity in catalytic reactions, and may also provide promising templates to grow nanostructures.« less
  • No abstract prepared.
  • The pressure controlled oxygen reordering processes in REBa{sub 2}Cu{sub 3}O{sub 6+x}(RE = Y,Nd,La) causing the continuous charge transfer between the CuO{sub x} and CuO{sub 2} planes were investigated. The charge transfer results in the time evolution of superconductivity. A strong acceleration of ordering and disordering processes was found when the RE-ion size increases from Y to La. Pressure induced semiconductor-superconductor transition in LaBa{sub 2}Cu{sub 3}O{sub 6+x} resulted from the oxygen ordering is reported for the first time.
  • No abstract prepared.