Non-destructive compositional depth profile in the tens-of-nanometer scale

Non-destructive compositional depth profile determination in the tens-of-nanometer scale is a challenging issue. In the present study we present a methodology based on the tunability of the sampling depth by changing the electron kinetic energy of the photoelectron from a sample constituent chemical element. This methodology profits from the variable energy excitation capability of a synchrotron X-ray source and from the feasibility of hard X-rays to create high kinetic energy electrons. The analysis of electrons with kinetic energies up to 15 keV enables the access to interfaces buried by several tens of nanometers. We demonstrate that in the case of stacking layers the proposed method enables the determination of the interface depth and roughness with high accuracy and enables the detection of chemical inter-diffusion of few monolayers width. The proposed method is also well suited to chemical diffusion inside a compound where the density contrast is extremely low to apply, for instance, the X-ray reflectivity technique.