Properties of organic specimens and their supports at 4 K under irradiation in an electron microscope.

Radiation damage is one of the most severe problems in the electron microscopy of organic materials. Observations which were made in an electron microscope with a superconducting lens system have shown that the damage caused by the electron beam is considerably reduced by one to two orders of magnitude if the specimen is cooled to liquid helium temperature (4.2 K). This cryoprotection is even higher in favorable cases, particularly when embedded specimens are used. The cryoprotection decreases for specimens mounted on plastic carrier films due to the low thermal and electrical conductivity of these materials at low temperatures.