REFINEMENT OF THE ${\rm{Si}}(111) \mbox{-} (\surd{3} \times \surd{3}){\rm{R30}}^\circ - {\rm{Ag}}$ STRUCTURE BY LOW-ENERGY ELECTRON DIFFRACTION

1995 ◽  
Vol 02 (04) ◽  
pp. 451-457 ◽  
Author(s):  
H. OVER ◽  
S.Y. TONG ◽  
J. QUINN ◽  
F. JONA
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Bond Length ◽  
Debye Temperature ◽  
Low Energy ◽  
Energy Electron ◽  
Data Set ◽  
Low Energy Electron Diffraction ◽  
The Third ◽  
Low Energy Electron

We have reinvestigated the bond geometry of the [Formula: see text] surface by means of low-energy electron diffraction using a much larger experimental data set than that previously used. The [Formula: see text] surface consists of a [Formula: see text] lattice of Ag atoms which replaces the topmost Si atoms, and forces the remaining Si atoms to form trimers. The Ag-Ag bond length turned out to be 3.47±0.12 Å. The Ag atoms are laterally displaced from the bulk positions of the Si atoms which they have replaced by 0.53 Å resulting in a Ag-Si bond length of 2.36±0.17 Å. The missing top Si layer and the formation of Si trimers lead to strong distortions in deeper Si layers, most notably a buckling in the third and fourth Si layer with a magnitude of about 0.35 Å and 0.2 Å, respectively. Applying the concept of ‘split positions’, the low Debye temperature of Ag has been interpreted as being caused by strong in-plane (either static or dynamic) movements of the Ag atoms perpendicular to the Ag-Si bonding.

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

STRUCTURE OF Ag{410}

1999 ◽  
Vol 06 (03n04) ◽  
pp. 355-359 ◽  
Author(s):  
F. JONA ◽  
P. M. MARCUS ◽  
E. ZANAZZI ◽  
M. MAGLIETTA
Keyword(s):  
Electron Diffraction ◽  
Computer Program ◽  
Interlayer Spacing ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
The Third ◽  
Stepped Surface ◽  
Low Energy Electron ◽  
Program Change

A quantitative low-energy electron diffraction (QLEED) analysis of data collected from a clean Ag{410} surface finds no relaxation of the first interlayer spacing, 36% compression of the second interlayer spacing and 18% expansion of the third interlayer spacing with respect to the bulk value (0.496 Å). The Ag{410} surface is a stepped surface with the smallest interlayer spacing analyzed so far by QLEED with the computer program CHANGE. Some difficulties in the analysis are discussed.

DETERMINATION OF THE SURFACE-BARRIER IMAGE-POTENTIAL ORIGIN ON Cu(001) FROM VERY LOW-ENERGY ELECTRON DIFFRACTION

1999 ◽  
Vol 06 (05) ◽  
pp. 635-643 ◽  
Author(s):  
M. N. READ
Keyword(s):  
Electron Diffraction ◽  
Image Plane ◽  
Low Energy ◽  
Energy Electron ◽  
Surface Barrier ◽  
Energy Position ◽  
Data Set ◽  
Low Energy Electron Diffraction ◽  
A Value ◽  
Low Energy Electron

A set of experimental very low-energy electron diffraction VLEED intensities on Cu(001) for angles of incidence of 35°, 40°, 50°, 60°, 70° and 80° in the (11) azimuth obtained by Dietz, McRae and Campbell has been analyzed using a surface-barrier model which allows for the angle and energy dependence of both the saturation from the image form and the height of the barrier potential. All three parameters of the potential form were allowed to vary independently. It is found that a fit between experiment and theory of the energy position of all the features (minima and maxima) in the entire data set to ≤ 0.07 eV can be obtained with the image-plane origin at z0=-1.70± 0.05 Å from the center of the first row of atoms with a barrier height U0 increasing in energy from 11.6 eV with respect to the muffin-tin zero at 35° incidence to 13.1 eV at 80°. The saturation from image form is found to show no trend in variation with respect to the energy or angle of approach of the electron to the barrier and has a value of UD=5.4± 1.0 eV with respect to the vacuum level at the jellium discontinuity. The value of z0 and barrier form found here differs from that of previous work of others and the analysis uses the largest VLEED data set to date.

Structural Analysis of a Cs + O Coadsorption Phase on a Ru(0001) Surface

1995 ◽  
Vol 50 (4-5) ◽  
pp. 453-458 ◽  
Author(s):  
M. Gierer ◽  
H. Bludau ◽  
H. Over ◽  
G. Ertl
Keyword(s):  
Structural Analysis ◽  
Electron Diffraction ◽  
Bond Length ◽  
Hard Sphere ◽  
Unit Cell ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
Sphere Radius ◽  
Low Energy Electron

The adsorption of oxygen onto a Ru(0001)-(2 x 2)-Cs phase with coverage ΘCs = 0.25 gives rise to the formation of a Ru(0001)-(2√3 x 2√3)R30°-3Cs-20 coadsorption structure with three cesium and two oxygen adatoms in the unit cell. A low-energy electron-diffraction (LEED) analysis reveals that oxygen is located in threefold hollow sites on the Ru surface while the Cs atoms remain near on-top sites; this site was also found in the pure Ru(0001)-(2 x 2)-Cs phase. The oxygen-Ru bond length of (2.14 ± 0.05) Å is longer by 0.11 A than in the Ru(0001)-(2x2)-0 phase, indicating that the Ru-O bond is weakened in the presence of coadsorbed Cs. The Cs hard sphere radius of (1.75 ± 0.07) Å is close to the ionic Pauling radius of 1.69 Å

Low-Energy-Electron-Diffraction Structural Studies of (100) Cleavage Surfaces of In4Se3 Layered Crystals

2014 ◽  
Vol 59 (6) ◽  
pp. 612-621 ◽  
Author(s):  
P.V. Galiy ◽  
◽  
Ya.B. Losovyj ◽  
T.M. Nenchuk ◽  
I.R. Yarovets’ ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Low Energy ◽  
Energy Electron ◽  
Structural Studies ◽  
Low Energy Electron Diffraction ◽  
Layered Crystals ◽  
Low Energy Electron

The role of an energy-dependent inner potential in quantitative low-energy electron diffraction

2000 ◽  
Vol 458 (1-3) ◽  
pp. 155-161 ◽  
Author(s):  
S Walter ◽  
V Blum ◽  
L Hammer ◽  
S Müller ◽  
K Heinz ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Low Energy ◽  
Energy Electron ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Energy Dependent
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