Features

Rotating the sample improves the depth resolution in high performance dynamic SIMS measurements by minimising the evolution of surface topography. This otherwise develops in one of two ways. On single crystal samples, usually semiconductors, bombardment with an energetic non-normal primary beam causes ripples to develop in the surface. Normal incidence avoids this effect but is not possible in the Cameca IMS.

Very low primary beam energies also help but create problems in spot size and erosion rate. Sample rotation is a more practical method for eliminating this problem. The second mechanism occurs on polycrystalline materials, for example metallisations on semiconductors, where severe surface topography is caused at all incident angles and energies of the primary beam by the different erosion rates of the randomly orientated crystallites. In this case the roughening can be greatly reduced only by the combination of sample rotation and non-normal incidence.