Analysis of solid surfaces with high sensitivity, and with a broad dynamic range, is important to a number of technologies, including semiconductor processing and heterogeneous catalysis. In this research project supported by the Analytical and Surface Chemistry Program, a picosecond laser will be used to ionize species directly above a solid surface, and then analyze them by time of flight mass spectrometry. These species will be desorbed by ion beam or laser beam interaction with the surface being analyzed. The objectives of this research program are to develop this surface analysis method by carefully characterizing the photoionization process, measuring velocity and angular distributions of sputtered particles, and by determining detection sensitivity factors and relative neutral and ion fraction sputtering yields. In order to detect low levels of contaminants on semiconductor surfaces, or to identify low coverage species in catalytic systems, it is necessary to have available very sensitive surface analytical tools. This research program is designed to develop and perfect a very sensitive photoionization probe of surface composition. A fast laser pulse will be used to ionize ion or laser desorbed species, and mass spectrometry will be used to detect and identify the ions. This approach promises a significant increase in surface analytical sensitivity over presently available methods.
