PtSi/n-Si(100) diodes were prepared by sputter-deposition of Pt where some of the Si substrates had previously been subjected to a strong plasma cleaning. Samples were investigated by I–V measurements, deep-level transient spectroscopy, and ballistic electron emission microscopy (BEEM). As a result of the strong plasma cleaning, both I–V and BEEM showed the Schottky barrier to be substantially reduced by about 0.2 eV as compared to very mildly plasma-cleaned samples. We present a model for the BEEM spectra which takes image force correction and tunneling across the metal/semiconductor interface into account. These effects occur because of the high electric field near the interface due to donor-type defects introduced by the plasma cleaning.