Damage formation and annealing studies of low energy ion implants ...

Figure 4.7 a) Plot of a Gaussian distribution b) The
error function in MEIS spectra is typically of the form
of the integral of the Gaussian distribution. The
standard deviation is indicated. From (4).
The second effect referred to earlier is the system resolution. Many parts of the
system are subject to statistical fluctuations of some kind. It is convenient to lump
together the fluctuations from the major experimental causes. This is close to a
Gaussian distribution and can be characterised by the standard deviation Ωr, commonly
referred to as the system resolution. The main contribution to the system resolution is
the energy resolution of the detector. At the Daresbury facility ∆E/E is ~ 0.35%. Other
contributions to the system resolution include the energy spread in the analysing beam,
the acceptance angle of the detector and the width of the beam. The energy resolution is
the most significant contributor.
In the same way as the depth scale is calculated, the depth resolution can be
calculated by applying the energy error of the analyser. The resolution is dependent on
the scattering configuration but a depth resolution of 0.6 nm is typical (17). To improve
the overall depth resolution, scattering configurations that result in long pathways
through the sample are used. Using a beam energy where the rate of energy loss is high
also improves the resolution. This means that better resolution is achieved with He
compared to H. The absolute error of the detector is reduced using lower beam energies,
and hence lower beam energies can improve the resolution.
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