Spectrofluorometric probe methods are developed and examined regarding their ability to model preferential solvation around probe molecules in binary solvents. The first method assumes that each fluorophore is solvated by only one type of solvent molecule and that each fluorophore contributes to the emission intensity. Expressions for this model are illustrated using fluorescence behavior of pyrene, benzo[e]pyrene, benzo[ghi]perylene, and coronene dissolved in binary n-heptane + 1,4-dioxane and n-heptane + tetrahydrofuran mixtures. The second method treats the solvational sphere as a binary solvent microsphere, with the fluorophore's energy in both the ground and the excited states mathematically expressed using the "nearly ideal binary solvent" (NIBS) model. Expressions derived from this model are illustrated using fluorescence behavior of 9,9'-bianthracene and 9,9*-bianthracene-10-carboxaldehyde in binary toluene + acetonitrile and dibutyl ether + acetonitrile.

Tungsten metal is used as an electrical conductor in many modern microelectronic devices. One of the primary motivations for its use is that it can be deposited in thin films by chemical vapor deposition (CVD). CVD is a process whereby a thin film is deposited on a solid substrate by the reaction of a gas-phase molecular precursor. In the case of tungsten chemical vapor deposition (W-CVD) this precursor is commonly tungsten hexafluoride (WF6) which reacts with an appropriate reductant to yield metallic tungsten. A useful characteristic of the W-CVD chemical reactions is that while they proceed rapidly on silicon or metal substrates, they are inhibited on insulating substrates, such as silicon dioxide (Si02). This selectivity may be exploited in the manufacture of microelectronic devices, resulting in the formation of horizontal contacts and vertical vias by a self-aligning process. However, reaction parameters must be rigorously controlled, and even then tungsten nuclei may form on neighboring oxide surfaces after a short incubation time. Such nuclei can easily cause a short circuit or other defect and thereby render the device inoperable. If this loss of selectivity could be controlled in the practical applications of W-CVD, thereby allowing the incorporation of this technique into …