X rays have many advantages over electrons and other charged particles for the microcharacterization of materials. X rays are more efficient in photoejecting inner shell electrons which results in characteristic x-ray fluorescence. X rays also produce less Bremsstrahlung which yields far higher signal-to-background than obtained with electrons. Minimum detectable limits (MDL) for X ray excited fluorescence can be a few parts per billion; 10{sup {minus}3} to 10{sup {minus}5} less than for electron excitation. The third generation synchrotron radiation sources such as the Advanced Photon Source will for the first time provide x-ray sources as brilliant as the most advanced electron probes. It will therefore soon be possible to develop a submicron x-ray probe with unprecedented low levels of detection in diffraction, EXAFS, Auger, Photoelectron and fluorescence spectroscopies for structural and chemical characterization. Some applications to materials science are shown
