Sputtering of Single-Element Targets

Mean Number of Emitted Atoms Incident Particle 

The sputtering process involves a complex series of collisions (the collision cascade) involving a series of angular deflections and energy transfers between many atoms in the solid. The most important parameter in the process is the energy deposited at the surface. 

The sputtering yield is proportional to the number of displaced or recoil atoms. In the linear cascade regime, which is a reasonable approximation for medium mass ions (such as Ar), the number of recoils is proportional to the energy deposited per unit depth in nuclear energy loss. The sputtering yield, Y, for particles incident normal to the surface is then expressed as (Sigmund 1981) 

The material factor A in (12.2) contains the material parameters and is a description of the number of recoil atoms that can escape from the solid. In Sigmund s description (1981) 

For calculation purposes, use values of a from Fig. 12.3, Uq in eV, dE/dx in eV nm and N in atoms nm Examples of this calculation for the sputtering of Si are shown in Fig. 12.2 along with experimental data and sputtering coefficients determined using Monte Carlo simulations. 

Sputtering is the erosion of a sample by energetic particle bombardment and is characterized primarily by the sputtering yield, Y, which is defined as 

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