Artifacts in Secondary Electron Emission Yield Measurements

Measurement of secondary electron yields and electron energy distributions appears straightforward--simple equipment, simple electronics, easy-to-acquire data, at least in a laboratory setting. Unfortunately, the low secondary electron energy (2-5 eV) and the extreme sensitivity of the yield to surface condition and surrounding environment make the measurement details anything but simple. These problems affect the accuracy and interpretation of the experimental results, often in a subtle way. Most troublesome is the production of unwanted (and unexpected) secondary electrons from within the electron sources and detectors, and tertiary electrons from the surrounding vacuum chamber environment. In addition, the sample surface condition can change during measurement, for example, through electron damage or enhanced oxidation/carburization. Electron source, analyzer, and sample effects will be discussed with examples for oxidized Al, niobium, graphite, gold and, also, TiN coatings.