Energy Dispersive X-Ray Reflectivity (EDXRR) - X-ray reflectivity is a technique for measuring thin film roughness and layer thickness non-destructively.  The technique is highly sensitive and can measure RMS surface roughness as low as 0.1 nm.  By using energy dispersive detection and a broad-band x-ray source, the reflectivity spectrum is obtained more rapidly than by conventional angle scanning means.  Full XRR spectra have been obtained in only 20 s from metal films on oxidized Si.  This rapid acquisition makes it possible to monitor the evolution of the surface during growth or sputter etching, as well as to look at reactions at buried interfaces during annealing.  The measurements in figure 4 show the kinetics of the formation of a Al-Cr intermetallic during annealing of a layered Al/Cr/SiO2 structure.   Consumption of the Cr layer can lead to deadhesion of the film.  Note that the measurements were obtained from one sample in real time; similar results using ex situ techniques would require multiple samples.