Radiation damage and sputtering

The sputtering process is used deliberately in secondary ion mass spectrometry (SIMS) [48] not only to remove atoms from the surface and to identify them by measuring their mass but also to gradually erode the surface to probe the composition in depth (chemical depth-profiling). In LEIS, the goal is to make the measurement before damage or sputtering can alter the structure or composition of the surface. 

More recently, techniques have been developed to make SIMS more sensitive by ionizing the removed neutral component using either a plasma or lasers. The laser ionization can be made particularly sensitive as powers and frequency control are 

An expression for the sputter yield Y E[, 9 ) [4S-50] (number of sputtered atoms per incident particle as a function of energy and incident angle) provides an insight to the processes involved. 

9 is measured relative to the surface normal and 9 80°, and Uq is the surface binding energy, which is usually taken as the sublimation energy. 

Typical values of the sputter coefficient range from 0.1 to 10 for most apphcations however, there are situations in which it is orders of magnitude greater than this. 

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