The provision of accurate composition-depth profiles to depths >1 p m is important in the characterization and investigation of thick films, surface coatings, surface treatments and many other technologically important applications. At present, such profiles are usually achieved by sequential ion bombardment and surface analysis and hence involve many difficulties in interpretation due to the non-uniform erosion of surfaces under ion bombardment. in this paper a method of obtaining accurate depth profiles is described using a ball-cratering device. The method employs a rotating ball to fashion a well-defined spherical crater in the sample surface, the depth and width of which can be accurately controlled. The specimen is then cleaned in situ using a scanning ion beam for a short period and the composition-depth profile is obtained either by point-by-point analysis down the sloping sides of the crater wall or by using Auger line-scan techniques across the crater. Coating-su'bstrate interface analysis can also be obtained by sputter-depth profiling at a point on the coating close to the exposed substrate. The method is not only considerably faster than ion etching, but the resulting depth profile also has a well-defined depth resolution. Composition-depth profiles through nitrocarburized mild steel surfaces and protective surface coatings are presented to illustrate the usefulness of the technique.

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