Superior Imaging Quality of Scanning Helium-Ion Microscopy: a Look at Beam-Sample Interactions,

D Cohen-Tanugi, N Yao
2009 Microscopy and Microanalysis  
Scanning Helium-Ion Microscopy (SHIM) offers high-resolution imaging at the sub-nanometer scale. SHIM is characterized by the high brightness of its ion source, its high secondary electron yield as well as the deep penetration of He + ions. However, studies thus far have not placed sufficient emphasis on the reasons for such behavior or on the energy-dependence of SHIM resolution. In this presentation, we will provide new understandings on these questions by investigating the characteristics of
more » ... characteristics of the beam-sample interaction involved in SHIM, and compare it with those of Scanning Electron Microscopy (SEM) and Scanning Gallium Ion Microscopy (SGIM). The collisions between ions and sample atoms can be statistically treated as two independent types of events: electronic collisions and nuclear collisions [1] . In an electronic collision, the ion is said to scatter inelastically from the atom, exciting a secondary electron (SE) in the sample atom and losing energy in the process, but maintaining its original direction since its mass is much larger than the electron mass. In a nuclear collision, the ion scatters elastically without exciting any electrons. Here we define the interaction radius R as the radius inside of which secondary electrons escape the solid, centered at the position of the incident beam.
doi:10.1017/s1431927609098687 fatcat:p53mgvev4jctbment5ov6a2zdq