Aluminum Oxide Replicas for Electron Microscopy Produced by a Two-Step Process

A two-step method is described for preparing aluminum oxide replicas of aluminum and non-aluminum specimens. In this method a thick layer of aluminum is evaporated onto the surface to be studied and pulled off the surface with Scotch Tape or cement covered glass. Aluminum oxide is formed on the side of the aluminum film which has been in contact with the specimen by anodizing in 3 percent ammonium tartrate at about 40 volts. The aluminum oxide film, which represents a positive replica of the specimen surface, is released from its substrate in dilute hydrochloric acid, washed with distilled water, and mounted for the electron microscope investigation. The applicability of the described method is demonstrated with electron micrographs of various specimens. The aluminum oxide films produced in ammonium tartrate are free of pores and grain structure. Films only 100 to 150A in thickness can be prepared and are suitable as temperature resistant supporting membranes for electron microscope and electron diffraction investigations.