PROBABILITY-DISTRIBUTIONS OF ENERGY DEPOSITION AND IONIZATION IN SUBMICROMETER SITES OF CONDENSED MEDIA

A general analytic approach is developed for calculating both the ener gy deposition distributions and the ionization distributions produced by ions incident on target sites with dimensions that range from micro meters down to a few nanometers. The effect of target geometry, energy -loss straggling, transport of energy from the site by secondary elect rons and Fano fluctuations on the ionization distribution is clearly d elineated as a function of target size. As an example, the ionization distributions produced by 1 MeV protons randomly incident on small sph erical sites of silicon are calculated. The approach should be useful in a wide variety of research areas including radiation effects in mic roelectronics, microlithography, radiation biology and thermoluminesce nce dosimetry.