Non-destructive chemical analysis of sandwich structures by means of soft X-ray emission

Soft X-ray emission spectroscopy provides information about elemental compo sition, including the light elements, as well as the chemical bonding. The probe depth reaches hundreds of nanometers but under certain conditions con siderable surface sensitivity can be attained. For electron impact excitati on, the probe depth can be varied by variation of the electron energy, and by Variation of the detection angle. The highest surface sensitivity is obt ained when the emission angle is near the critical angle for total reflecti on. In this case the effective probe depth is of the order of a few wavelen gths, typically around 3 nm for 3d transition element L emission. In the pr esent study we show the feasability of using the angular dependence as a me ans to study the thickness and composition of layered samples by comparing the experimental data to model calculations based on the X-ray optical cons tants of the constituent materials. (C) 1999 Elsevier Science S.A. All righ ts reserved.