Elementary Steps in Plasma Chemistry

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In this project in the Experimental Physical Chemistry Program, John Moore and John Tossell of the University of Maryland will investigate the processes involved in electron-molecule collisions. Such processes include: dissociative electron attachment, yielding a radical and a negative ion; direct dissociation, resulting in two radicals; dipolar dissociation, resulting in the simultaneous production of a positive and a negative ion; and dissociative ionization, yielding an ion and a radical. The project involves both experimental and theoretical characterization of such processes as they occur in the gas phase as well as on surfaces. Systems chosen for study include halocarbons, halosilanes, halogenated alkenes, and halofluorocarbons. These precursors and their products are thought to be crucial in understanding the chemistry involved in plasma reactors such as those used for plasma etching and in the fabrication of semiconductor devices. An electrical discharge in a gas creates an electron-rich environment which induces chemical changes in normally unreactive gases. This highly charged mixture is known as a plasma, and the chemical reactions taking place are termed plasma chemistry. Such reactors have found widespread use in the semiconductor industry for fabrication of both materials and devices. This research will provide detailed information on the nature of the species involved in such reactions, as well as fundamental knowledge of their reactions.