The absorption spectra of the gases ethylene-do, d I' I, I-d" cis-d" trans-d" d 3 , and d 4 have been photographed using the first order of a 21-ft vacuum spectrograph. Analyses of both the Rydberg system at 1750 A and the 7r*-7r system between 1500 and 2100 A have been extended. Band contour analysis has confirmed the assignment of the Rydberg system as I B 3" _IA g' The resulting rotational constants of the 4 2 level of the excited state of C,D 4 lead to an inertial defect indicative of a non planar molecule. Assuming point group D" we have combined the constants with Franck-Condon calculations in a complete structure determination for the 4' level of the Rydberg state: rcc=1.41 A, r cH =1.08 A, ~ HCH=124.4° and an azimuthal angle of 31'. Linewidths in the successful simulation of the C,D 4 0--0 band indicate a lifetime greater than 10-13 sec for molecules in the zero level of the Rydberg state. For the 7r*-7r system, all observed bands for all molecules studied have been assigned. Most striking is the relative inactivity of the C-C stretching vibration; except in C,D 4 , only the torsional mode is active. It is concluded that r cc for the 7r*-7r state is not very different than it is for the Rydberg state. Finally, the extrapolation to the (unobserved) origin of the 7r*-7r system is revised to give 5.5 eV (2285 A).

Carbon-doped SiO2 low k thin films were prepared by radio frequency plasma-enhanced chemical vapor deposition at 400°C from polymerization of tetramethylsilane (4MS) and copolymerization of tetramethylsilane and silane false(SiH4false) precursor, with nitrous oxide as the oxidant gas. Copolymer thin films from 4MS and SiH4 precursor show much higher deposition rates than polymer thin films from 4MS, if all other parameters are kept the same. The addition of SiH4 can significantly promote the plasma polymerization of 4MS. The structure and composition of these films were characterized using Fourier transform infrared and X-ray photoelectron spectroscopy. The physical properties of the films have been investigated by dielectric constant, refractive index, and thermal stability measurements. The two kinds of films have similar chemical composition and structure. The film as prepared shows excellent thermal stability at temperatures as high as 400°C and a dielectric constant of about 3, which indicates that it has potential as a low k dielectric for advanced interconnect applications. © 2001 The Electrochemical Society. All rights reserved.

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