Surface Chemistry Studies with Cluster Ion Beams

在化学系化学测量和成像计划的支持下，宾夕法尼亚州立大学的Nicholas Winograd教授和他的团队专注于阐明高能粒子与固体相互作用的基本方面，目的是提高二次离子质谱仪(SIMS)实验的实用性。这项研究的结果将在聚合物科学、天体物理、药物发现、有机电子学、有机光伏和分子特定成像等不同领域找到材料表征应用。C60等团簇离子源的出现为分子深度剖析提供了独特的机会。在这种情况下，分子固体的层被簇源去除，没有明显的化学损伤积累，深度分辨率小于10 nm。这种模式提供了以前所未有的空间分辨率审问埋藏界面的可能性。分子特异性成像是SIMS的另一个独特功能，当与分子深度剖析相结合时，可以产生化学成分的三维渲染。优化这些实验的协议将从对星团轰击事件的计算机模拟的预测中开发出来，并通过在模型系统上进行实验来开发，其中可以系统地检查许多参数，如弹丸能量和角度。特别强调的是描述现在产生超过2000个原子的Ar团簇的气体团簇离子束的特征，以及寻找可以通过动态产生的预先形成的离子来增强电离的新的含氢物种。因此，最终目标是获得对团簇-固体相互作用的基本了解，并提供一种新的基于质谱学的、在纳米尺度上运行的三维成像协议。这一新的方法应该会在生物学家和材料科学家中找到有价值的应用，用于表征目的。该项目将包括三名研究生的参与，他们将开发用于成像和团簇离子束的新型仪器。他们将获得一些技能，这些技能将成为他们研究生生涯中的宝贵财富。在整个工作中，双重强调的是对离子-固体相互作用的基本了解，以及利用这些信息来推进应用。这一理念为该项目带来了协同效应，并为参与者提供了独特的学习体验。还建议通过SEECoS计划向高中生提供国际合作和外展服务。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Nicholas Winograd and his group at Pennsylvania State University focus on elucidating the fundamental aspects of the interaction of energetic particles with solids, with the goal of advancing the utility of secondary ion mass spectrometry (SIMS) experiments. Results from this research should find materials characterization applications in such diverse fields as polymer science, astrophysics, drug discovery, organic electronics, organic photovoltaics and molecule-specific imaging. The emergence of cluster ion sources such as C60 has opened unique opportunities in molecular depth profiling. In this situation, the layers of a molecular solid are removed by the cluster source without significant accumulation of chemical damage and with a depth resolution of less than 10 nm. This modality offers the possibility of interrogating buried interfaces with unprecedented spatial resolution. Molecule-specific imaging is another unique feature of SIMS, and when combined with molecular depth profiling, yields a 3-dimensional rendering of the chemistry. Protocols for optimizing these experiments will be developed from predictions of computer simulations of the cluster bombardment event, and by performing experiments on model systems where a number of parameters, such as projectile energy and angle, can be systematically examined. A special emphasis is placed upon characterizing gas cluster ion beams that now produce argon clusters with more than 2000 atoms, and on searching for new H-containing species that may enhance ionization through dynamically created pre-formed ions. The ultimate goal, then, is to acquire a fundamental understanding of cluster-solid interactions and to provide a new mass spectrometry-based 3-dimensional imaging protocol that operates on the nanoscale. This new methodology should find valuable applications to a wide range of biologists and material scientists for characterization purposes. The project will include participation of three graduate students who will develop novel instrumentation for imaging and for cluster ion beams. They will acquire skills that are designed to be valuable assets in their post-graduate careers. Throughout this effort, dual emphasis is placed upon acquiring a fundamental understanding of ion-solid interactions, and of utilizing this information to advance the applications. This philosophy lends a synergism to the program and provides a unique learning experience for those involved. International collaboration and outreaching to high school students through the SEECoS program are also proposed.