scholarly journals A Leed Investigation of (111) Oriented Si, Ge and GaAs Surfaces Following Pulsed Laser Irradiation

1980 ◽  
Vol 1 ◽  
Author(s):  
D. M. Zehner ◽  
J. R. Noonan ◽  
H. L. Davis ◽  
C. W. White ◽  
G. W. Ownby
Keyword(s):  
Electron Diffraction ◽  
Ruby Laser ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Low Energy ◽  
Ultra High Vacuum ◽  
Surface Structures ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Pulsed Laser Irradiation

ABSTRACTThe low energy electron diffraction (LEED) patterns obtained from clean (111) oriented Si, Ge and GaAs single crystals subsequent to their irradiation with the output of a pulsed ruby laser in an ultra-high vacuum (UHV) environment suggest that metastable (1×1) surface structures are produced in the regrowth process. Conventional LEED analyses of the Si and Ge surfaces suggest that they terminate in registry with the bulk but that the two outermost interlayer spacings differ from those of the bulk. For the case of Si these changes are a contraction of 25.5 ± 2.5% and an expansion of 3.2 ± 1.5% between the first and second and second and third layers respectively.

Mirror Electron Microscope-Low Energy Electron Diffraction for Studies of Surface Ordering and Melting

1990 ◽  
Vol 208 ◽  
Author(s):  
W. N. Unertl ◽  
C. S. Shern
Keyword(s):  
Electron Diffraction ◽  
Surface Potential ◽  
High Vacuum ◽  
Normal Incidence ◽  
Low Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

ABSTRACTMirror Electron Microscopy – Low Energy Electron Diffraction (MEMLEED) combines a LEED with MEM in a single simple instrument for studies of surface processes such as phase transitions and premelting under ultra-high vacuum (uhv) conditions. In MEMLEED, 5–20 keV primary electrons are decelerated by an electrostatic mirror-objective lens in which the sample is the mirror element. In the MEN mode, electrons are reflected just above the surface, reaccelerated through the objective lens and imaged. Contrast is due to variations in both surface potential and topography. Current uhv instruments have lateral resolution of about 1 μm. In the LEED mode, 0-100 eV electrons strike the sample at near normal incidence. Diffracted electrons are accelerated through the objective lens. Beam spacings in the imaged diffraction pattern are proportional to k11 and beams do not move as the incident energy is varied. MEMLEED has intrinsically higher transfer width and is less sensitive to magnetic fields near the sample than conventional LEED. Design considerations for uhv instruments are discussed. Applications to the study of order-disorder transitions, premelting phenomena, and to measurements of changes in surface potential are described.

scholarly journals Surface crystallography with low-energy electron diffraction

1993 ◽  
Vol 442 (1914) ◽  
pp. 61-72
Keyword(s):  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Low Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
X Ray ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Surface Crystallography

Bragg’s 1913 publication of the principles of X-ray crystallography came only a year after von Laue’s discovery of X-ray diffraction from crystals. Structure determination (of small molecules) with high-energy electron diffraction followed by just three years the 1927 discovery of electron diffraction by Davisson and Germer. By contrast, low-energy electron diffraction (LEED) would require four more decades before yielding its first structure determinations (of surfaces) around 1970. The delay was primarily due to the need for ultra-high vacuum and to a lesser extent to the need for a suitable theory to model multiple scattering. This review will sketch the development of surface crystallography by LEED and describe its principles and present capabilities.

scholarly journals Growth of germanium on Au(111): formation of germanene or intermixing of Au and Ge atoms?

2017 ◽  
Vol 19 (28) ◽  
pp. 18580-18586 ◽  
Author(s):  
Esteban D. Cantero ◽  
Lara M. Solis ◽  
Yongfeng Tong ◽  
Javier D. Fuhr ◽  
María Luz Martiarena ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Scanning Tunneling Microscopy ◽  
High Vacuum ◽  
Low Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron

We studied the growth of Ge layers on Au(111) under ultra-high vacuum conditions from the submonolayer regime up to a few layers with Scanning Tunneling Microscopy (STM), Direct Recoiling Spectroscopy (DRS) and Low Energy Electron Diffraction (LEED).

THE CASE FOR ORDER-N METHODS IN LEED THEORY

1997 ◽  
Vol 04 (05) ◽  
pp. 901-905
Author(s):  
J. B. PENDRY
Keyword(s):  
Electron Diffraction ◽  
Point Source ◽  
Surface Structure ◽  
Time Evolution ◽  
Low Energy ◽  
Surface Structures ◽  
New Approach ◽  
Low Energy Electron Diffraction ◽  
Low Energy Electron ◽  
Moderate Complexity

Low energy electron diffraction experiments have superb sensitivity to surface structure, but rely on sophisticated theory for their interpretation. Advances in computer power, and developments in the theory itself, enable us to handle surface structures of moderate complexity. For future advances we must look to a completely new approach and the case is made for order-N methods which follow the time evolution of a point source of electrons to generate all beams for all angles of incidence and all energies in one shot.

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