N:Si ratio

In general, an increase in rf power density decreases the Si/N ratio in the film (227-229). Because the binding energy of the Si-H bond is less than those of the N-H and N-N bonds, an increase in rf power should increase the concentration of reactive nitrogen species relative to the number of reactive silicon species and thereby decrease the Si/H ratio in the film. At high power densities and at high temperatures, the Si/N ratio approaches 0.75, which is the stoichiometric ratio for Si3N4. 

CaSi2 reacts with ammonium halides to calcium halide and a silicon nitride with an Si N ratio of 3 l253- ... 

We observe that as the partial pressure of NH3 is increased, the amount of hydrogen incorporated into the film rises from 14 to 26 atomic %. The film density is a maximum where the Si/N ratio is 0.75. 

Figure 8 Silicon nitride film density as a function of Si/N ratio for different diluents.4 Reprinted by permission of the publisher, The Electrochemical Society, Inc.

Summary Polysilacarbosilanes and polysilasilazanes prepared according to a copolymer strategy offer an easy, coherent approach to polycarbosilanes and silazanes, precursors of SiC and SiCN-based materials with variable C/Si and C/Si/N ratios. In contrast with the polysilazane route which leads, upon pyrolysis, to carbon-containing silicon nitride, the synthesized polycarbosilazanes are finally converted into nitrogen-containing silicon carbide. 

Dortch, Q., Rabalais, N. N., Turner, R. E., and Qureshi, N. A. (2001). Impacts of changing Si/N ratios and phytoplankton species composition. In Coastal Hypoxia Consequences for Living Resources and Ecosystems (Rabalais, N. N., and Turner, R. E., eds.). American Geophysical Union, Washington, DC. Coastal and Estuarine Studies 58, pp. 37—48. 

Strongly suggesting that anthropogenic changes in Si N ratios have directly selected for this cosmopolitan diatom. The recent evidence from China (Zhao et ai, 2005) suggests that these patterns are not isolated to the Louisiana shelf... 

Sommer, U. (1994a). Are marine diatoms favoured by high Si N ratios Mar. Ecol. Prog. Ser. 115, 309v-315v. 

Sommer, U., Hansen, T., Stibor, H., and Vadstein, O. (2004). Persistence of phytoplankton responses to different Si N ratios under mesozooplankton grazing pressure A mesocosm study with NE Atlantic plankton. Mar. Eco. Prog. Ser. 278, 67-75. 

Impact of iron on silicon pumping. Iron limitation of diatoms increases the pumping of silicon (relative to nitrogen and carbon) to deeper waters. Iron-limited diatoms are inhibited in their utihzation of nitrogen as a result of the iron requirement of nitrate reductase (Geider and LaRoche, 1994). However, iron-limited diatoms continue to take up silicic acid, although at lowered rates (De La Rocha et al., 2000). As a result, the Si N ratios of iron-limited diatoms... 

Thus, the decrease in the dissolved Si N ratio of river water might explain an alleged increase in the frequency of non-diatom blooms in coastal waters. 

Figure 5-19. Variation of Si/N ratio in PECVD films of SiiN4 as a function of deposition temperature for different SiH4/NHj ratios (Data from [149, 150. ...

For comparison values for Si3N4 films prepared by atmospheric-pressure CVD at 900°C from SiH4, NH3, N2 gas mixtures are also listed. Microchemical analysis data have shown that the chemical composition of the plasma silicon nitride films is slightly Si-rich at a Si/N-ratio between 0.8 and 1.0 compared to 0.75 for stoichiometric deposits. As indicated by infrared spectrometry, there are also larger amounts of hydrogen and traces of oxygen in the films. Therefore the true film composition may be represented by SxNyHz [195]. Films deposited at 300°C are thermally stable up to about 400°C. As a consequence of compressive film stress, blis-... 

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