The depth resolution of composition-depth profiles obtained by ball-cratering and Auger electron spectroscopy

Abstract

The provision of accurate composition-depth profiles to depths 1 μm is important in the characterization and investigation of thick films, surface coatings, surface treatments and many other important applications. Profiles to these depths are best achieved by mechanically tapering the surface and ball cratering has been shown to be a convenient and accurate method. The ball cratering instrument employs a rotating steel ball, coated with fine diamond paste, to abrade a well-defined spherical crater in the sample, the depth and width of which can be accurately controlled. The specimen is then clean, in situ, using a scanning ion beam and the profile is obtained by point-to-point Auger analysis down the sloping sides of the crater wall.The depth resolution of the depth profiles obtained by ball cratering depends on the crater geometry, the diameter of the probing beam and the extent of the mechanical roughness produced by the wear process. In this paper, experiments are described in which a hard chrome coating, 6 μm in thickness, on a polished mild steel substrate is used as a model system for a series of measurements aimed at defining the depth resolution as a function of the operating parameters.