Atomic Structure of Binary Alloy Surfaces

1986 ◽  
Vol 83 ◽  
Author(s):  
H. L. Davis ◽  
J. R. Noonan
Keyword(s):  
Atomic Structure ◽  
Binary Alloys ◽  
Low Energy ◽  
Metallic Surfaces ◽  
Surface Layers ◽  
Low Energy Electron Diffraction ◽  
Specific Effects ◽  
Ordered Alloys ◽  
Low Energy Electron ◽  
Structure Of Alloy

ABSTRACTAfter discussions of multilayer relaxation for monatomic metallic surfaces and low-energy electron diffraction (LEED) procedures, some available results concerning the atomic structure of alloy surfaces are reviewed briefly. Results are discussed only for surfaces of ordered binary alloys and crystalline, substitutionally random binary alloys. Surfaces for which detailed results are available are highlighted as examples which illustrate some general crystallographic effects that occur at alloy surfaces. Specific effects included in the examples are the rippling of atomic constituents in the surface layers of ordered alloys, the preferential termination of alloys by a specific type of layer where more than one type of layer exists in the bulk, a mixture of two possible terminations, and the alternating enrichment and depletion of an atomic constituent in the surface layers of alloys which are disordered in the bulk.

CHEMICAL RECONSTRUCTION OF THE TiAl(010) SURFACE

1995 ◽  
Vol 02 (02) ◽  
pp. 183-189 ◽  
Author(s):  
C.P. WANG ◽  
S.K. KIM ◽  
F. JONA ◽  
D.R. STRONGIN ◽  
B.-R. SHEU ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Atomic Structure ◽  
Atomic Layer ◽  
Interlayer Spacing ◽  
Low Energy ◽  
Intensity Analysis ◽  
Low Energy Electron Diffraction ◽  
Surface Phases ◽  
Low Energy Electron ◽  
Bulk Structure

The atomic structure of a clean (010) surface of the ordered binary alloy TiAl (with tetragonal bulk structure of the CuAu I type) is studied with quantitative low-energy electron diffraction (QLEED). Two different surface phases are found depending on the preparation procedure. After a cleaning step in vacuo by means of Ar-ion bombardments, anneals at 750−850°C produce a 2×1 surface and anneals at about 900° C produce a 1×1 surface. A QLEED intensity analysis of the 1×1 structure reveals the occurrence of chemical reconstruction, whereby the Ti atoms in the first layer exchange places with the Al atoms in the second layer. Thus, while any bulk (010) plane contains 50% Al and 50% Ti , the top atomic layer of a (010) surface contains 100% Al and the second atomic layer contains 100% Ti . Both layers are slightly buckled and the first interlayer distance is compressed about 7.1% while the second interlayer spacing is expanded about 7.4% with respect to the bulk value.

STRUCTURE OF A SINGLE-ATOMIC LAYER OF COBALT ON THE Pt(111) SURFACE: A STUDY BY QUANTITATIVE LOW-ENERGY ELECTRON DIFFRACTION

1995 ◽  
Vol 02 (03) ◽  
pp. 279-283 ◽  
Author(s):  
ANDREA ATREI ◽  
MONICA GALEOTTI ◽  
UGO BARDI ◽  
MARCO TORRINI ◽  
ERMANNO ZANAZZI ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Atomic Structure ◽  
Room Temperature ◽  
Atomic Layer ◽  
Crystallographic Analysis ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

The atomic structure of the surface formed by depositing a single-atomic layer of cobalt on Pt (111) has been investigated using low-energy electron diffraction (LEED) crystallographic analysis. Cobalt grows at room temperature on the Pt (111) surface forming islands a single-atomic layer thick. The layer is ordered and it forms a 1×1 epitaxial phase where cobalt atoms are in an fcc registry with respect to the substrate.

scholarly journals Surface Structural Analysis of the Layered Perovskite Ca1.9Sr0.1RuO4 by Low Energy Electron Diffraction I-V

2018 ◽  
Vol 7 (1) ◽  
pp. 56-62
Author(s):  
Ismail Ismail ◽  
Rongying Jin ◽  
David Mandrus ◽  
Earl Ward Plummer
Keyword(s):  
Electron Diffraction ◽  
Bond Length ◽  
Atomic Structure ◽  
Room Temperature ◽  
Low Energy ◽  
Energy Electron ◽  
Layered Perovskite ◽  
Plane Rotation ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

Abstract – The atomic structure at surface of the layered perovskite Ca1.9Sr0.1RuO4 has been studied by Low Energy Electron Diffraction (LEED) I-V. The perovskite Ca1.9Sr0.1RuO4 of single crystal was cleaved in ultra high vacuum chamber (the pressure in the chamber was about 1x10-10 Torr). The experiments were conducted at room temperature (T=300 K). The sharp LEED pattern was observed which indicates that the surface of Ca1.9Sr0.1RuO4 is flat and it is a well ordered crystal. LEED I-V data, nine equivalent beams of the layered perovskite Ca1.9Sr0.1RuO4 were recorded at room temperature. LEED I-V calculation was performed to fit experimental data to obtain the surface atomic structure. The LEED I-V analysis reveals that in the surface of the layered perovskite Ca1.9Sr0.1RuO4 the RuO6 octahedra are rotated (in-plane rotation) alternating clockwise and counterclockwise. The in-plane rotation at the surface is 11 degree which is smaller than that in the bulk (13 degree). The Ru – O(1) bond-length at the surface is found to be 1.936 Å which is about the same as in the bulk (1.939 Å). The Ru – O(2) bond length at the surface is 1.863 Å which is much shorter than that in the bulk (2.040 Å). The volume of octahedral Ru-O6 at the surface is reduced by 9% with respect to the bulk. This finding shows that the atomic structure at surface of the layered perovskite Ca1.9Sr0.1RuO4is significantly different than that in the bulk. These lattice distortions strongly influence its electronic properties.   Key words: Transition Metal Oxide; Perovskite; Surface Atomic Structure; LEED I-V

THE ATOMIC STRUCTURE OF Si(111)-$(\sqrt{3}\times\sqrt{3})$R30°-Ga DETERMINED BY AUTOMATED TENSOR LEED

2000 ◽  
Vol 07 (03) ◽  
pp. 267-270 ◽  
Author(s):  
WENHUA CHEN ◽  
HUASHENG WU ◽  
WING KIN HO ◽  
B. C. DENG ◽  
GENG XU ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Atomic Structure ◽  
Atomic Layer ◽  
Low Energy ◽  
Wide Energy Range ◽  
Low Energy Electron Diffraction ◽  
Wide Energy ◽  
Low Energy Electron ◽  
Vertical Spacing ◽  
Iv Curves

The atomic structure of the Si (111)-[Formula: see text]R30°-Ga surface has been studied by comparing measured low-energy electron diffraction (LEED) intensity (IV) curves with calculated IV spectra using the method of automated tensor LEED. The experimental LEED IV curves used in this work contain many beams and a wide energy range. The results show that the Ga atoms occupy T4 sites, at 2.62 Å above the second-atomic-layer Si atoms. The Ga–Si vertical spacing is 1.44 Å and the bond length between the Ga atom and the first-layer Si atom is 2.52 Å. Large bucklings are found in the first and second Si bilayers below the adatom layer.

ATOMIC STRUCTURE OF A {001} SURFACE OF THE ALLOY FeRh

1999 ◽  
Vol 06 (01) ◽  
pp. 133-136 ◽  
Author(s):  
S. KIM ◽  
F. JONA ◽  
P. M. MARCUS
Keyword(s):  
Electron Diffraction ◽  
Surface Structure ◽  
Atomic Structure ◽  
Atomic Layer ◽  
Interlayer Spacing ◽  
Low Energy ◽  
Low Energy Electron Diffraction ◽  
Cscl Type ◽  
Low Energy Electron ◽  
Bulk Structure

The atomic structure of a {001} surface of the ordered binary alloy FeRh (with bulk structure of the CsCl type) is studied with quantitative low energy electron diffraction. The {001} surface structure is found to be bulklike (1× 1), with the first atomic layer 100% Rh and the second 100% Fe. The first interlayer spacing is contracted by 9.8% with respect to the bulk value (1.4935Å) and the second interlayer spacing is slightly expanded by 2.4%.

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