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Chemical Vapor Deposition ͑CVD͒ of silicon dioxide from tetraethoxysilane ͑TEOS͒ and ozone was modeled using CHEMKIN-III simulation software. Modeling assumed that film growth proceeds via the fast oxidation of silicon-bearing compounds by ozone or atomic oxygen at the substrate surface. The objective of the study was to use kinetic data from the literature to develop a reliable reaction model with no more than one adjustable parameter. The simulations established that direct contribution of TEOS surface reactions to film growth is negligible in TEOS/ozone CVD. Depositions at low TEOS flow rates are controlled by diffusion of intermediate silicon-containing compounds formed in the gas phase by reaction of TEOS with atomic oxygen. The depletion of ozone or atomic oxygen within the reactive boundary layer becomes rate limiting at high TEOS flows, while gas-phase polymerization reactions reduce the rate at high pressures. Close agreement with the published rate data was obtained for reactions at 643 K but discrepancies remain at higher deposition temperatures. It is believed that the model overpredicts the formation rate of intermediates at high temperatures because the mechanism fails to fully account for gas-phase oxidation reactions between atomic oxygen and the organic fragments from TEOS oxidation reactions.

Microcontact printing techniques employing self-assembled alkanethiol monolayers in the production of metal masks have been combined with CFalOz reactive ion etch for subsequent pattern transfer to silicon. Silicon feature sizes of about 300 nm have been demonstrated. Some inadequacies in the self-assembled monolayers (SAMs)-formed metal masks have been characterized by electron microscopy. Pafiicularly, nickel etch control and metal feature edge definition remain problems to be solved if the process is to be employed in submicron feature production. Nickel patterns produced in the process and used as masks without the gold overlayer were successful as masks in the reactive ion etching (RlE) process. They also appear to give a somewhat improved edge definition over processes in which the gold layer remains.

S,142+(AsF,-), has been prepared and its crystal structure determined in which the S,1,,+ cation was found to have a distorted right triangular prismatic structure, with one S, and two I, units joined by weak sulphuriodine bonds; the sulphur-sulphur bond distance is the shortest reported in an isolated compound, and is indicative of the presence of a 3p7r-3pw bond and a bond order greater than two.

Inorg. Chem. 1981, Acknowledgment. Thanks are expressed to Dr. B. E. Mann, University of Sheffield, for running some 31P N M R spectra. Registry No. I, 78355-34-7; 11, 78355-36-9; [(np3)Pd(P4)], 78 3 5 5-3 7-0; [ Pt (P3) (triphos)] BF4, 78 3 5 5-3 9-2; [ Pd2( P3) (np,) 2 ] B F4, 20, 3839-3845 3839 78355-41-6. Supplementary Material Available: Listings of structure factor amplitudes (22 pages). Ordering information is given on any current masthead page.S71AsF6 and S71SbF6 were prepared essentially quantitatively by a variety of routes. Attempts to prepare S8I+ salts were unsuccessful. S7ISbF6 crystallizes in the orthorhombic space group P212121 with a = 11.786 (2) A, b = 9.187 (1) A, c = 12.400 (3) A, and ddCd = 2.90 Mg m-3 for Z = 4. The structure has been determined by multiple-solution direct methods and refined by least squares to final agreement indices R , = 0.046 and R2 = 0.061 for 1628 independent reflections with 11. 2a(I). S7IASF6 crystallizes in the triclinic space group Pi with a = 15.516 (1 1) A, b = 11.813 ( 8 ) A, c = 11.650 (8) A, a = 107.30 (4)", @ = 74.71 (S)', y = 104.62 ( S ) ' , and dald = 2.78 Mg m-3 for Z = 6. The structure was refined to a final agreement index R = 0.14. The s71+ cations in both salts and in (S71)4S4(A~F6)6 are essentially identical. S71+ contains a seven-membered sulfur ring with a slightly twisted chair conformation, similar to that of S7, with an exocyclic iodine, and has a geometry similar to that of S 7 0 . The sulfur-iodine bond length is 2.342 (3) A and corresponds to a bond order of 1. The sulfur-sulfur distances within the ring vary from 1.906 ( 5 ) to 2.389 (4) A. There is one short intracationic iodine-sulfur contact of 3.394 (3) A. The geometry and bond length variations in S71+ are discussed and compared with those of related systems. Some experimental observations on & ( A s F~)~, 19 I x 2 16, are presented and the nature of these species is discussed. IntroductionGenerally any pair of main-group elements, excepting those of group 8A, form binary compounds or alloys. At one time sulfur and iodine were thought' to be one of the pairs of elements that were an exception to this generalization. Since then, evidence has been presented for sulfur iodides prepared at low temperatures, although they are unstable under ambient conditions. Solid S212 has been characterized at -90 "C by its infrared and electronic ~p e c t r a ,~.~ and infrared evidence has been presented4 for SI2 isolated in an argon matrix at 9 K. An attempted preparation of SI3+ (cf. Se13+) led instead5 to the relatively stable S71MF6 (M = As and Sb) salts, containing a binary sulfur-iodine cation, and a full account of this work is reported below. Subsequently, [(S71)21] (SbF6)3-2AsF3 and S214(AsF6)2,7 which also contain stable sulfur-iodine cations, were prepared and characterized.The ability of sulfur to catenate is well established; however,