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

Published online by Cambridge University Press:  21 February 2011

W. N. Unertl  and
C. S. Shern
W. N. Unertl
Affiliation:
Laboratory for Surface Science & Technology, Univ. of Maine, Orono, ME 04469
C. S. Shern
Affiliation:
Dept. of Physics, National Taiwan Normal University, Taipei, Taiwan 11718
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Abstract

Mirror 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.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 208: Symposium J – Advances in Surface and Thin Film Diffraction , 1990 , 261
Copyright
Copyright © Materials Research Society 1991

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