Review Lecture - Perspectives in high voltage electron microscopy

Abstract

The initial impetus for using higher voltages in electron microscopy came from a desire to examine specimens thicker than could be satisfactorily imaged at 100 kV. Microscopes operating at voltages as high as 3 MV are now in regular use. In metallurgy they are pro­viding valuable information on radiation damage and other dynamic processes. The study of reactions in a controlled gaseous environment is a new development. In biology, much has been learnt about the optimum thickness of specimen for image clarity and information content. A promising application is to the study of the structure of chromosomes. Radiation damage has little visible effect on gross detail in desiccated material, but it limits the observation of living specimens. Attempts are now in progress to attain the higher resolving power made available by the shorter wavelength of fast electrons. The atomic architecture of macromolecules could in theory be laid bare, but it may be confused by radiation damage.