Absolute total and partial electron impact ionization cross sections of hexamethyldisiloxane

被引:74
作者
Basner, R
Foest, R
Schmidt, M
Becker, K
Deutsch, H
机构
[1] Inst Niedertemp Plasmaphys, D-17489 Greifswald, Germany
[2] Stevens Inst Technol, Dept Phys & Engn Phys, Hoboken, NJ 07030 USA
[3] Univ Greifswald, Inst Phys, D-17489 Greifswald, Germany
基金
美国国家科学基金会;
关键词
hexamethyldisiloxane; electron impact ionization; cross sections; plasma polymerization;
D O I
10.1016/S1387-3806(98)14027-7
中图分类号
O64 [物理化学(理论化学)、化学物理学]; O56 [分子物理学、原子物理学];
学科分类号
070203 ; 070304 ; 081704 ; 1406 ;
摘要
We studied the electron impact ionization of hexamethyldisiloxane (HMDSO), Si2O(CH3)(6), which is widely used in plasma-enhanced polymerization applications. Appearance energies and absolute partial cross sections for the formation of fragment ions with relative intensities >1% of the most abundant ion, the Si2O(CH3)(5)(+) fragment ion, were measured in a high resolution double focusing sector field mass spectrometer with a modified ion extraction stage far electron energies from threshold to 100 eV. Dissociative ionization was found to be the dominant process. The main ionization channel removes a complete methyl group to produce the fragment ion Si2O(CH3)(5)(+) with a cross section of 1.7 x 10(-15) cm(2) at 70 eV. The stoichiometric and isotope composition of the various fragment ions was determined by using the high resolution (m/Delta m = 40,000) of the mass spectrometer used in these studies. The methyl ion is formed with considerable excess kinetic energy, whereas all other fragment ions are formed with essentially no excess energy. The experimental total single ionization cross section of HMDSO (2.2 x 10(-15) cm(2) at 70 eV impact energy) is in good agreement with the result of a semiempirical calculation (2.1 x 10(-15) cm(2) at the same energy). (C) 1998 Elsevier Science B.V.
引用
收藏
页码:245 / 252
页数:8
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