Low-Energy Electron-Molecule Interactions

马里兰大学帕克分校的约翰·摩尔和约翰·托塞尔得到了实验物理化学计划的支持，该计划研究低能电子与多原子分子和分子碎片相互作用时导致化学变化的过程中的离散步骤。在低能电子束穿过气相靶的实验中，将检查分子和分子自由基上的解离电子附着体。将开发技术来产生和定量检测气相中的自由基。此外，还将研究电子撞击吸附在金属和半导体表面上的分子所引起的解离和随后的化学反应。将进行量子化学计算来描述目标分子和自由基的相关电子性质，选择这些分子和自由基是因为它们与等离子体化学处理以及电子束和离子束沉积有关。预计结果将提供定量信息，如横截面，这些信息可以对工业制造技术的建模和优化产生有用的影响。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，它们是通常只有在非常高的温度下才能发现的化学活性物种。这种从相对良性的起始材料在低温下产生具有侵略性的化学物种，解释了在许多工业制造技术中开发低能电子碰撞过程的原因。例如，在集成电路制造中，用于清洗、蚀刻和沉积的电子束和离子束光刻以及等离子体和化学工艺。

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.