This Major Research Instrumentation RUI award is for the development and construction of an improved Nuclear Reaction Analysis (NRA) detection system based upon the Alabama A&M coincidence scheme, but with one to two orders of magnitude improvement in the signal-to-noise ratio. Previous results indicate that by modifying the detector geometry and materials, a larger, more efficient detector is possible without increasing the background signal. By using sample cooling and beam rastering, this larger detector will be able to routinely profile hydrogen in semiconductors with a sensitivity of one part-per-million and a surface depth resolution of five nanometers while remaining compatible with existing IBA facility requirements. The development of this detector would likely increase the use of NRA in the materials characterization community since it could be easily added to any existing IBA facility with minimal cost. This would allow companies and universities to perform hydrogen profiling by NRA and to use NRA for calibrating other IBA techniques including SIMS. Finally, the detector's ability to dramatically reduce all background sources including competing nuclear reactions without the reduction in efficiency of a germanium detector should open up new opportunities for profiling other light elements including nitrogen, boron, and carbon with greatly improved sensitivities.
Light trace elements are known to have dramatic effects on the electrical, chemical and mechanical properties of many types of materials in even minute quantities. NRA is a powerful ion beam technique for quantitatively profiling light impurities in materials with excellent depth resolution. NRA has previously been used to profile a wide range of trace elements including H, B, C, N, and F in problems ranging from hydrogen embrittlement of metals to the dating of arrowheads. Potentially important applications of NRA include passivation studies of SiO2/SiC and SiO2/Si interfaces using hydrogen or nitrogen and the profiling of carbon and boron in metals to test predictions of computer simulations. Presently, few electronic companies or universities have NRA capability due to the technical difficulties inherent in obtaining high sensitivity.
