ION-BEAM ETCHING TECHNIQUE IN THE PREPARATION OF SAMPLES FOR CROSS-SECTIONAL MICROSCOPY STUDIES OF THIN-FILMS AND HARD COATINGS

The scanning tunneling microscope has proved to be an effective tool i n the structure characterization of interfaces and interlayers in thin films and coatings. However, since it lacks the deep profiling capabi lities sufficient to penetrate hard coatings, an ion beam etching meth od has been developed for cross-sectional sample preparation. The samp le preparation method is developed keeping in mind the image formation of a scanning tunneling microscope which is based on the topographica l differences of the inspected surface. Thus the sample preparation pr ocess includes three main parts. Firstly, a mechanical grinding and po lishing step, secondly, an ion beam polishing step for producing a smo oth surface and, thirdly, an ion beam etching step for producing a top ography related to the bulk microstructure of the sample. Examples of results obtained with TiN hard coatings are given, including X-ray sca nning force microscopy pictures of a tribofilm grown on a TiN-coated c ast iron sample during a high temperature wear test; the usefulness of the developed technique is discussed. The results achieved are compar ed with the structural information obtained by X-ray transmission elec tron microscopy analysis from the same samples.