New rapid and accurate method to measure low-energy-electron-diffraction beam intensities: The intensities from the clean Pt (111) crystal face

The intensities of the low-energy-electron-diffraction beams backscattered from the clean platinum (111) surface are measured by a photographic technique. The fluorescent screen in a conventional low-energy-electron-diffraction chamber is photographed at various incident electron energies in electron-volt intervals in the range of 20-200 eV. The film is then machine developed and scanned using a computer-controlled digital-output microdensitometer. The intensity profiles of all of the diffraction beams can be obtained simultaneously this way in ten minutes and these are identical to those measured by telephotometer. The film can readily monitor three orders of magnitude change in intensity. The photographic diffraction-beam-intensity measurement is particularly useful when time-dependent changes in the beam intensities due to adsorption, chemical reactions or electron-beam-surface interactions occur or when many diffraction beams are present as in the case of coincidence lattices or reconstructed surfaces. The diffraction beams from the clean platinum (111) crystal face have been measured by both photography and telephotometry and the intensity profiles necessary to carry out surface-structure analysis are reported.