Design and construction of a RHEED diffractometer with energy resolution capability

In this work the author describes the set up of a UHV system to study the growth of ultra-thin metallic films on a silicon substrate under RHEED conditions. However, a new feature has been added to the normal RHEED apparatus. Because the phosphor screen acts as a high pass filter for the scattered electrons, energy filtering is normally excluded from RHEED techniques. In the experimental apparatus, a biased Faraday collector has been added to measure only the elastically scattered part of the diffracted beams. The electrical currents involved range from about 15 nA to 0.1 nA for the elastically scattered part of a diffracted beam. The (111) surface of Si has been chosen to perform RHEED, with the incident beam along the (100) direction. In order to test the performance of the RHEED set-up, the authors have performed two kinds of measurements, first, they have deposited Ag/Si(111) at different rates and have monitored the diffracted current of the specularly reflected beam with the Faraday collector unbiased, and second, they have tested the capability of the Faraday cup to measure only the elastically scattered part of the diffracted beams