Surface Analytical Chemistry with Intense Picosecond Laser Light

具有高灵敏度和宽动态范围的固体表面分析对包括半导体加工和多相催化在内的许多技术都很重要。在这个由分析和表面化学项目支持的研究项目中，将使用皮秒激光直接在固体表面上电离物质，然后用飞行时间质谱法分析它们。这些物质将被离子束或激光束与被分析表面相互作用解吸。本研究计划的目标是通过仔细表征光电离过程，测量溅射粒子的速度和角分布，并通过确定检测灵敏度因子和相对中性和离子分数溅射收率来发展这种表面分析方法。为了检测半导体表面上的低水平污染物，或识别催化系统中的低覆盖物质，有必要使用非常敏感的表面分析工具。本研究计划旨在发展和完善一种非常灵敏的表面成分光电离探针。快速激光脉冲将用于电离离子或激光解吸物质，质谱法将用于检测和识别离子。与目前可用的方法相比，这种方法有望显著提高表面分析灵敏度。

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.