Impurity-Movement Problems in Analysis Methods Using Particle Bombardment

Abstract

Most of the analysis methods described in this book rely upon the use of charged-particle beams of either ions or electrons to produce secondary species or radiation which on detection reveals the constituents of the materials under analysis. Two generic types of analysis may be distinguished: (1) those in which the bulk is analyzed directly, and (2) those in which the surface is analyzed directly and the bulk characteristics are determined by profiling either by the use of the analyzing beam or by the use of an auxiliary sputtering beam. Typical of the first type would be electron probe microanalysis (see Chapter 18), in which an electron beam of energy of the order of 20 keV is used to excite fluorescent x rays from the solid under analysis. The range of such electrons is of the order of a few micrometers. Analysis methods of the second type include ion microprobe microanalysis (see Chapter 21), ion-scattering spectrometry,(1) Auger electron spectroscopy (see Chapter 20), and SCANIIR (see Chapter 23). The assumption made in many of these analysis methods is that the beam does not disturb the distribution of elements in the solid which is being analyzed. For many methods which use charged-particle beams, this is not, in fact, the case. In this chapter we will discuss the ion-migration problems which may occur in all these methods of surface analysis.