The ability to quantitatively measure trace concentrations in microvolume samples is quite important in the expanding areas of thin film and microelectronic device technologies. Equally important is the ability to obtain chemical composition vs. sample depth information. Some example applications include electrical contacts and lead bonding where impurities at the interface may have significant effects on adhesion, junction devices in which one would like to have an abrupt chemical transition from one material to another, epitaxial film growth, and diffused and implanted devices in which the dopant distribution profiles may differ from simple theory due to lattice strain, electric field enhancement and other effects.