Specimen damage caused by the beam of the transmission electron microscope, a correlative reconsideration

Abstract

From physical and chemical studies of radiation, we found that under the conditions of routine electron microscopy massive amounts of energy are absorbed by the specimen. Chemical studies have demonstrated that such ionizing radiation produces characteristic alterations: cross-linking, scission, mass loss, and crystal destruction. During routine study the temperature of the thin organic electron microscopic specimen apparently does not rise much more than 100°C. Although there has been extensive theoretical consideration, temperature conditions—heat production and dissipation—have been inadequately defined for the electron microscope proper. The chemical changes that occur on irradiation describe average changes for a large number of molecules. It is not possible to predict the behavior of one particular molecule by using the results obtained from irradiated gross material. Estimates indicate that radiation damage affects the molecular structure of the object at the 1–4 A level. For a given rate of energy input the specimen appears to alter and then assume a steady state at which it can dissipate incoming energy nondestructively. With present-day knowledge of beam-specimen interaction, it does not seem feasible to observe living material in conventional or high-voltage electron microscopes for any practical period of time. The mechanism of chemical changes occurring in a high dose-rate radiation environment, heat production, and dissipation in the specimen during irradiation, and the nature of the physical-chemical steady state of the specimen during observation should be subjects of further studies.