low-­energy electron microscopy abbr., LEEM (rus. микроскопия медленных электронов) — a branch of microscopy involving low-energy elastically backscattered electrons for imaging of solid body surfaces.

Description

Low-energy electron microscopy was invented by Ernst Bauer in the early 1960s, and has been widely used in surface research since the 1980s. In a microscope, primary low-energy (up to 100 eV) electrons are emitted onto a subject surface, and the electrons reflected from the surface are focused to create a magnified image of the surface. This type of microscope has a spatial resolution of as much as several dozen nanometres. Image contrast depends on the variations of a surface's ability to reflect slow electrons due to differences in crystal orientation, surface reconstruction or coverage. While microscopic images may be generated very quickly, low-energy electron microscopy is often used to examine dynamic processes occurring on different surfaces, including the growth of thin films, etching, adsorption and phase transitions in real time. In illustration thereof, the figure shows a microscopic image of the surface of Si(111) during phase transition from reconstruction 7×7 to reconstruction 1×1 occurring in an environment with temperature of 860° С.

Illustrations

Microscope image of slow electrons in the phase transition from 7x7 reconstruction to 1x1 recon
Microscope image of slow electrons in the phase transition from 7x7 reconstruction to 1x1 reconstruction on the Si(111) surface. The 7x7 phase (bright sections) decorates atomic stages, while the surface of terraces is mostly covered with the 1x1 structure (dark sections). Image field size is 5 um [2].

Authors

  • Zotov Andrey V.
  • Saranin Alexander A.

Sources

  1. Oura K. et al. Surface Science: An Introduction // Springer, 2010 - 452 pp.
  2. Tromp R.M. Low energy electron microscopy // IBM J. Res. and Develop. 2000. V. 44. P. 503–516.

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