Electron Impact Ionization of SiClx and TiClx ($x = 1--4$): Contributions from Indirect Ionization Channels

概要

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We measured absolute partial cross sections for the formation of various singly charged positive ions produced by electron impact on SiClx ($x = 1--4$) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast neutral beam apparatus. In the case of SiCl4, the absolute cross sections obtained by the two different experimental techniques were found to agree very well. The ionization of the SiClx ($x = 1--3$) free radicals can only be studied using the fast-beam technique. Some of the partial cross section curves were found to exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV, which is in some cases followed by a shallow minimum at about 40 eV and a broad second maximum at around 100 eV. This pronounced low-energy maximum is indicative of the presence of an indirect ionization channel and is similar to what has been observed earlier for TiCl4 and the TiClx ($x = 1--3$) radicals. Similarities in the contribution of the indirect ionization channel to the formation of the various SiClx+ and TiClx+ ($x = 1--4$) ions will be highlighted in this paper.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-10-30