Low-Energy Electron-Molecule Interactions

马里兰大学帕克分校的约翰·摩尔和约翰·托塞尔在实验物理化学项目的支持下，研究低能电子与多原子分子和分子片段相互作用时导致化学变化的过程中的离散步骤。在低能电子束通过气相靶的实验中，将研究分子和分子自由基的解离电子附着。在气相中产生和定量检测自由基的技术将得到发展。此外，电子对吸附在金属和半导体表面的分子的冲击引起的解离和随后的化学反应将被研究。量子化学计算将用于描述目标分子和自由基的相关电子特性，选择目标分子和自由基是因为它们与等离子体化学处理和电子束和离子束沉积有关。结果有望提供定量信息，如横截面，这可以对建模和优化工业制造技术产生有用的影响。电子和分子的低能碰撞会导致化学键断裂。这些相互作用的产物往往是自由基和离子，它们是通常只在非常高的温度下发现的化学活性物质。这种在低温下从相对良性的起始材料中产生侵略性化学物质的方法说明了在许多工业制造技术中低能电子碰撞过程的开发。例子包括电子和离子束光刻和等离子体和化学工艺用于清洗，蚀刻，和沉积在集成电路的制造。

John Moore and John Tossell of the University of Maryland, College Park, are supported by the Experimental Physical Chemistry Program to study discrete steps in the processes leading to chemical change when low-energy electrons interact with polyatomic molecules and molecular fragments. Dissociative electron attachment to molecules and molecular radicals will be examined in experiments in which a low-energy electron beam passes through a gas phase target. Techniques will be developed to produce and quantitatively detect radicals in the gas phase. In addition, dissociation and subsequent chemical reactions induced by electron impact upon molecules adsorbed onto metallic and semiconductor surfaces will be studied. Quantum chemical calculations will be carried out to describe the relevant electronic properties of target molecules and radicals, selected for their pertinence to plasma-chemical processing and electron-and ion-beam deposition. Outcomes are expected to provide quantitative information, such as cross sections, that can have useful impacts in modeling and optimizing industrial fabrication technologies. Low energy collisions of electrons and molecules can lead to chemical bond rupture. The products of these interactions tend to be radicals and ions, which are chemically reactive species that are ordinarily only found at very high temperatures. This creation of aggressive chemical species at low temperatures from relatively benign starting materials accounts for the exploitation of low energy electron collision processes in a number of industrial fabrication technologies. Examples include electron- and ion-beam lithography and plasma and chemical processes used for cleaning, etching, and deposition in the manufacture of integrated circuits.