The signal-to-damage ratio for microscopy based on electron loss by high-energy ions

Loss of one electron by singly charged ions is considered as a contrast mechanism for ion microscopy. At high energies, the mean free path for loss is comparable to specimen thicknesses and dependent on specimen atomic number. The ratio of electron loss events to atomic displacements in the specimen decreases with energy, and is estimated to be 500 for 1 MeV helium ions. The energy deposited in a molecule of adenine per electron loss event within the adenine is estimated to be less than 400 eV for 0.6 MeV nitrogen ions. This molecular dose is lower than is required for inelastic scattering of 2.5 keV electrons from the carbon K shell. (Auth.)