Radiation damage to organic and inorganic specimens in the TEM

Symptoms of radiation damage are reviewed, followed by a brief description of the three main damage mechanisms: knock-on displacement (predominant in electrically conducting specimens), ionization damage (radiolysis), and electrostatic charging effects in poorly conducting specimens. Measurements of characteristic dose and damage cross section are considered, together with direct and inverse dose-rate effects. Dose limited resolution is defined in terms of a characteristic dose and instrumental parameters. Damage control is discussed in terms of low-dose technique, choice of imaging mode, specimen temperature, specimen environment and TEM accelerating voltage. We examine the possibility of performing electron cryomicroscopy in STEM mode, with a judicious choice of probe current and probe diameter.