INVESTIGATION OF CONCENTRATION DEPTH PROFILES BY MEANS OF ANGLE-RESOLVED XPS - A POLYNOMIAL MODEL

This paper deals with the reconstruction of concentration depth profil es by means of angle resolved X-ray photoelectron spectrometry. A poly nomial model is introduced which describes the concentration distribut ion c(i)(x) of the element i as a polynomial of third order within the range 0 less-than-or-equal-to x less-than-or-equal-to x(m); x gives t he sample depth measured from the surface. The further constraints c(i )(x(m)) b(i) (with b(i) as the bulk concentration of the element i) an d dc(i)(x)/dx = 0 for x = x(m) reduce the number of unknown parameters to two per element with the additional parameter x(m) and the unknown photon flux. By means of computer simulation it can be shown that the results of the reconstructed depth profiles are stable and not very s ensitive to statistical errors of measured count rates. Experimentally measured count rates of an Al-Li alloy before and after segregation w ere evaluated. The calculation time per depth profile was approximatel y 10 min.