A simple mirror electron microscope–low-energy electron diffraction apparatus for surface studies

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Abstract
A new mirror electron microscope–low‐energy diffraction (MEM–LEED) apparatus based on previous designs has been constructed. In addition to its simplicity of fabrication, advantages of MEM–LEED over conventional LEED include: (1) A variable magnification, real‐space image of the surface is obtained. In our system, the magnification is 10–40. (2) The diffraction pattern is imaged on a flat screen and the spot spacings do not change with incident energy. Our instrument has a transfer width greater than 40 nm. (3) Only one vacuum port is required. (4) Changes in the surface potential are easily measured. (5) Large magnetic fields near the sample do not degrade the performance; for example, operation at 7‐eV incident energy in 10‐G fields is routine for our instrument. (6) Fabrication costs are low. In our MEM–LEED an 8‐keV primary beam is decelerated by a Johansson lens of which the sample forms the mirror element. The focal length is 25 cm. A major practical advantage in our MEM–LEED, unlike previous designs, is that the sample is near ground potential. The system is mounted through a 10‐cm‐diam port and is retractable. Examples of applications are given and the performance is demonstrated to surpass that of conventional display LEED systems.

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