Sputter Depth Profiling

Abstract

The understanding and modification of surface properties of materials often requires a detailed knowledge of the spatial distribution of specific elements in both the surface plane and as a function of depth normal to the surface. This chapter will concentrate on ways of analyzing depth distributions of elements, up to a few microns deep, using ion beam sputter profiling. Sputter profiling uses the combination of a surface sensitive analytical technique, such as SIMS, LEIS, AES, XPS or SNMS [4.1], together with the continuous exposure of a new surface by ion beam sputtering. The sputtering ion beam typically is Ar⁺, O ⁺₂ or Cs⁺ with energy in the range 1–20 keV, although other inert gas or liquid metal, Ga⁺ or In⁺, ion sources are also used, mostly for imaging. Ar⁺ is most commonly used with AES and XPS since it does not form compounds with target constituents and so does not significantly alter bulk atomic concentrations. O and Cs⁺ are favoured for SIMS since they increase secondary ion yields and reduce matrix effects. However, this is at the price of reduced sputter rates and profile distortion though compound formation and segregation. Profiling rates of up to 2 μm/h can be achieved although 0.1 μm/h is more typical.