ENERGY DEPOSITION IN THIN-FILMS CALCULATED USING ELECTRON-TRANSPORT THEORY

In scanning electron microscopy and low voltage point-projection micro scopy there is considerable interest in estimating beam damage which c an be related to the energy deposited in the specimen. We derive an ex pression for the energy deposition using the electron transport equati on and give results for beam energies of 1-10 kV incident on 100 and 2 00 nm carbon films. The elastic scattering was modeled using a Rutherf ord cross section; and the inelastic scattering cross section was deri ved from the Bethe stopping power equation. For the 100-nm-thick amorp hous carbon film 90% of the incident beam energy is deposited in the s ample at 2 keV, but at 6 keV only 20% of the energy is deposited. The 200 nm sample exhibited a similar curve with 20% deposition occurring at 9 keV. Our calculations show the same variation with beam energy as reported experimental results. (C) 1994 American Institute of Physics .