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Large Coherence Length Low Energy Electron Diffraction System using a Field-Emission Source

IP.com Disclosure Number: IPCOM000108658D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Hamers, RJ: AUTHOR

Abstract

Described is a low energy electron diffraction (LEED) system with a large coherence length and compact size. A field-emitter tip with an extremely small radius of curvature is used as the source.

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Large Coherence Length Low Energy Electron Diffraction System using a Field-Emission Source

       Described is a low energy electron diffraction (LEED)
system with a large coherence length and compact size.  A
field-emitter tip with an extremely small radius of curvature is used
as the source.

      In conventional LEED systems, the spatial coherence length is
approximately 100-200 Ao and is limited by the electron source.  In
prior art, field-emitter tips with very small end diameters (Z10 Ao)
which emit electrons into only a narrow cone angle (Z2o) have been
fabricated using field evaporating techniques.  The field-emitter
tips have been shown to be relatively stable even under high current
densities of several micro-amperes.  The small diameter tips provide
a long spatial coherence length, on the order of 15 microns at 150
eV, which is better than typical LEED electron guns.  The temporal
(longitudinal) coherence length can expect to be several thousand
angstroms.

      A LEED source using a 10-50 Ao diameter field emitter as the
electron source will have several unique properties. The predicted
long spatial and longitudinal coherence lengths make it possible to
investigate the ordering phenomena on much longer length scales (100
- 10,000 Ao) than conventional LEED systems can detect.  Ordering on
these longer length scales is considered important in epitaxy and
growth processes.  A LEED system based on such field-emitter tips can
also be made smal...