Electron mean free path (λa) has been investigated using Ballistic
Electron Emission Microscopy (BEEM). Using the average collector current computed from
large scale BEEM images and a model in which the current exponentially decreases in
terms of metal thickness, a constant value of λa = 11 nm has been calculated
in the 1–1.8 eV electron energy range. On small scale images, the study of
well-defined BEEM doMayns shows that either λa or the interface transmission
factor (or both) may differ from their average values. These local variations from one
grain to another are interpreted as interface defects and channeling of the electron
beam due to the electronic and crystallographic of the gold layer.