Evaluation of elastic emission machined surfaces by scanning tunneling microscopy

Elastic emission machining (EEM) developed by the authors is one of the atomic size machining methods. Roughness of the finished surface is as small as atomic size. It is also found that finished surfaces attain the perfection in the sense of physical properties to the extent of better than or comparable to chemically etched surfaces. EEM can be considered as a machining method utilizing chemical activities of ultrafine powder particle surfaces, instead of an etchant as in the conventional chemical etching. In this paper, the authors have developed a scanning tunneling microscope(STM) in order to evaluate the surfaces finished by EEM with the resolution of atomic size. STM measurements are carried out for the surfaces finished by EEM and by chemical etching. The result shows the existence of the micro pits with the diameter of 1 nm and the depth of 1 nm on the chemically etched surface. In contrast, neither pits nor projections are detected on the surface finished by EEM and an atomically smoothed surface is found to be established. The difference between the micro structure of the surfaces finished by EEM and by chemical etching is evident.