Exercise 1 solutions.
The right (high-energy) end of the graphs is from the surface of the Pt film. At this end the backscattered have maximum possible energy, as they have lost none in interactions with electrons while traveling through the sample. Therefore the energy loss of the ions originates solely from the backscattering.
(Not required to explain)
The scattering probability depends on inversely on the ion energy. The lower energy, the higher scattering probability. Thus, atoms deeper in the sample give higher intensity.
Yield ~ 1/E
The low-energy side of the graph originates from the Si-Pt interface, where the scattered ions have lost energy while traveling through the Pt film and back. The location of the low-energy side can be used to determine film thickness.
Dent at Pt/Si interface
Intensity peak decreases with annealing
(X-rays can also escape from the depths of the sample)