Full and Partial Particle Replication Technique for Electron Microscopy

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Abstract
The state of the art, and the principal problems of particle replication techniques have been reviewed. The objective was to obtain the highest reliability as well as the maximum geometrical and contrast resolution for the replication technique. To this end, further improvements and complementary developments of the now-known techniques of particle replication were made. The essential stages consist of: (1) preshadowing of the sample by a refractory alloy (Pt:10%Rh) evaporated in high vacuum from a carbon rod; (2) utilizing a residual gas scattering evaporation technique (carbon in an argon atmosphere of 10−3 mm Hg) at twice the mean free path of the carbon (this forms a thin uniform carbon coating layer as a supporting layer which gives a minimum of contrast in the electron microscope); (3) utilizing an auxiliary strengthening layer of a subliming material (sulfur) to protect effectively the replica from deformation or fracture during the preparation procedure (the auxiliary layer can later be removed by sublimation); (4) development of an easy to do partial-particle replication technique, utilizing a thermoplastic embedding technique to restrict replication to only one side of a particle which will give superposition free images.