The measurement of low mass surface constituents by medium energy time-of-flight forward recoil spectrometry.

摘要

A novel technique has been developed for determining the light element composition at or near the surface of a material. A time-of-flight spectrometer was constructed to detect the recoil particles ejected from a sample when probed by an energetic ion beam. The performance of this system for light element detection was evaluated for a wide range of analysis beams from helium to argon, at incident energies of 270 to 810 keV. The detection efficiencies for hydrogen, helium, carbon, and oxygen recoil species were experimentally measured over an energy range of 25 to 300 keV and a model describing the observed behavior was developed based on the physical processes governing time-of-flight detector response. The sensitivity and depth resolution were determined for near surface hydrogen and are equal to or better than typically achieved by standard analytical techniques. A number of materials of practical importance have been studied to establish the utility of the technique. Particular emphasis has been directed at the ion beam analysis and modification of nitrocellulose and Langmuir-Blodgett organic thin films.