Depth profiling energy calibration

Second, progress has been made in the theoretical approach to the analysis of DCEMS measurements. The underlying theory of resonance excitation (-> excitation matrix) in the sample by y-quanta including secondary absorption and emission processes, electron transport (- transport tensor), and detection response (—> response function) have been included in a least-squares fit routine [ 103. 105). Adjustable parameters in this fitting are. on the one hand, the hyperfine interaction and line shape variables, and, on the other hand, the variables that give a parametric representation of the depth profiles. The response parameters are also included to allow energy calibration of the experimental apparatus. 

In this idealized case, the profile can be obtained by varying the incident particle energy E0 stepwise within a certain interval. Yield calibration is done by a standard in an analogous way as described in equation (4). Close to the surface equation (5) can be simplified by the so-called surface approximation which consists in replacing S(E) by S(E0), i.e. by the value of the energy loss at the surface. The expression for the depth scale is then simply dR(E0) — (E0—ER)/S(E0). 

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