LOW-ENERGY-ELECTRON-DIFFRACTION SYSTEM USING A HIGH-PERFORMANCE ELECTRON-GUN AND POSITION-SENSITIVE DETECTORS

A new low-energy-electron-diffraction (LEED) instrument is described that combines resistive-anode-based position-sensitive detectors with a high-resolution electron gun capable of producing a beam having high spatial coherence (large instrument transfer width). The system produces digitized images of LEED patterns as well as high-resolution spot profiles of individual beams using incident currents in the picoampere range, thus vastly reducing or eliminating electron beam damage to sensitive surfaces. The display resolution of both spot profile and full display images is 10(24) X 10(24) channels, and the dynamic range is 16 bits ( almost-equal-to 10(4)) per channel. The resistive anode pulse processing electronics limits maximum data acquisition rates to 1 X 10(6) s-1. Specially developed software permits manipulation and numerical processing of the digitized two-dimensional images at full resolution to produce spot contour maps, spot line profiles along arbitrary directions, Fourier transforms of spot profiles, integrated spot intensities, and intensity vs voltage curves with suitably subtracted background.