INVESTIGATION OF THIN-FILMS BY SOFT-X-RAY FLUORESCENCE AND BY TOTAL ELECTRON YIELD MEASUREMENTS

We propose a description of the sampling depth (lambda) of total electron yield experiments (TEY) in terms of kinetic Auger electron energies. This empirical response results from literature data1-6 on low energy (< 2 keV) and from our own experiments performed on thin layers of Cu on Fe substrates and on thin layers of AlxGa1-xAs on GaAs substrates at energies of approximately 5 to 8 keV. From these investigations we estimate a sampling depth of 74 nm for Ga KLL Auger electrons in AlxGa1-xAs. For comparison, the sampling depth of x-ray fluorescence analysis (XRF) for Al Kalpha radiation in AlxGa1-xAs is 400 nm. Both methods (XRF and TEY) were joined for quantitative determination of the thickness t and the Al content x in thin AlxGa1-xAs layers on GaAs substrates. Al Kalpha fluorescence radiation excited by polychromatic x-radiation and the jump of the total electron yield in the vicinity of the GaK-edge were used in our analytical model. The validity of this model is verified by a comparison of our results with the expected values (known from preparation of the layers).