SEM Observation of Inclusions in Steel Samples Using Fast Cleaning and Modification of the Surface by Glow Discharge

SEM (scanning electron microscopy) is a useful technique for the observation of the surface morphology of various materials. Compared to TEM (transmission electron microscope), one of the advantages of SEM is easy sample preparation, although the spatial resolution of SEM is normally less than that of TEM. To improve the spatial resolution of SEM observation, it is well known that a low accelerating voltage SEM is an effective technique. We have proposed the application of glow discharge surface treatment before high-resolution SEM observation. An rf-glow discharge was applied with Ar gas for a steel sample just for 6 sec., leading to surface cleaning, that is, removing the surface oxidation or contamination layer. Besides the surface cleaning, a glow discharge sputtering modified the surface of the steel sample depending on crystal orientation. This surface modification was useful for high-resolution SEM observation. The surface of the steel sample was observed by FE (field emission)-SEM with a low accelerating voltage. A fine structure of grains and inclusions in the sample was clearly observed. The density of the inclusions was roughly determined as being 4 × 104/cm2.