A new pulse counting low-energy electron diffraction system based on a position sensitive detector

A new low-energy electron diffraction (LEED) system has been constructed with a pulse counting position sensitive detector using channel plates and a wedge and strip anode. The detector accepts diffracted electrons over a 120° angle and the LEED pattern is recorded as a 256×256 pixel image. Individual LEED spot intensities can be measured up to a maximum linear count rate of ∼5 kHz while the dark count rate is ∼0.02 Hz, yielding a dynamic range greater than 105. Incident beam currents for LEED measurements are ∼1 pA. Diffuse LEED intensities from disordered systems can be measured using the large dynamic range of this instrument. Examples of diffuse LEED measurements are presented. The low incident beam currents also allow for LEED intensity-voltage measurements on surfaces sensitive to electron beam damage and on nonconducting surfaces.