Low Energy Electron Reflection Microscopy (LEEM) and Its Application to the Study of Si Surfaces

Abstract

Low energy electron microscopy uses LEED beams to image surfaces and can either be done in the scanning mode (scanning LEED microscopy or SLEEM) [1] or in the true imaging mode (LEED)[2]. In LEEM the specimen is the cathode of an immersion lens — just as in an emission microscope — and is illuminated at (near) normal incidence by a (nearly) parallel low energy electron beam. The instrument can be operated either in the LEEM mode or -by imaging the back focal plane of the immersion lens onto the detector -in the LEED mode. Its resolution in the LEEM mode is in principle limited by the accelerating field in front of the specimen to 2 – 5 nm, depending upon electron energy, but at present only 15 nm has been achieved. The resolution in the LEEM mode (transfer width) is with the field emission gun of the order of 100 nm; at present 70 nm could be measured with a Si(111) crystal.

Dr. W. Telieps died in a tragic car accident on May 31, 1987. Starting from the basic instrument designed by G. Turner he succeeded in inventive, diligent and systematic work in making LEEM work. The publications referenced are an everlasting memorial for his scientific achievements.