Silanes partial

The decrease of the silane partial pressure and the concomitant increase of the hydrogen partial pressure as a function of plasma power can be understood in terms of the increased electron density and electron energy. Both lead to a higher dissociation of silane and hydrogen. The silane radicals and atomic hydrogen thus... 

In the deposition of a-Si H the dissociation of the process gas silane leads to the formation of hydrogen, disilane, trisilane, higher-order silanes, and a solid film. Silane is depleted. From the consumption of silane, one may estimate the deposition rate of the solid film. The difference in the silane partial pressure between... 

From an initial understanding of the silane kinetics, very little decomposition of the silane was expected at this (relatively) low surface temperature. Calculate the silane number-density field, assuming the nominal silane partial pressure at the inlet and for a temperature of 550°C. The measured number density just above the surface was 6 x 1015 molecules/cm3. What is the percent difference between the measured and ideal-gas result ... 

The reaction rate of the WF with silane is very fast. The hazard of an explosion may be overcome by low total pressure, low silane partial pressure, and fast flow rate. Silane reduction is only used for a short duration to initiate W nucleation and is followed by WF6/H2 reduction. 

Dispersion of NK and NP in polyolefins is not straightforward because of the polarity of these grades, so a silane coupling agent is recommended. TTie silane partially restores the elongation at break of PP, which can otherwise be drastically reduced by the FR, although impact strength as measured by Izod tests are maintained. 

Triphenylmethyl halides Halogenosilanes from silanes Partial replacement of Si-hydrogen by Si-halogen... 

Condensation catalysts include both acids and bases, as well as organic compounds of metals. Both tin(II) and tin(IV) complexes with carboxyhc acids ate extremely useful. It has been suggested that the tin catalyst is converted to its active form by partial hydrolysis followed by reaction with the hydrolyzable silane to yield a tin—sdanolate species (eqs. 22 and 23) (193,194). 

The partially alkoxylated chlorotitanates, (RO) TiCl, can be prepared in high purity by reaction of TiCl with an organosilane ester, Si(OR)4 (see Silicon compounds). The degree of esterification of the titanium can be controlled by the amount of silane ester used. When is 3 or 4, the addition of the appropriate alcohol and an amine receptor is required (5). 

The effective absorption of radiation by a gas can be increased by the addition of a sensitizer. For example, when mercuty vapour is added to silane gas, the mercury vapour absorbs radiation to form an excited atom Hg which collides with a silane molecule to lead to partial dissociation... 

While there is clear evidence for complex formation between certain electron donor and electron acceptor monomers, the evidence for participation of such complexes in copolymerization is often less compelling. One of the most studied systems is S-.V1 Al I copolymerization/8 75 However, the models have been applied to many copolymerizations of donor-acceptor pairs. Acceptor monomers have substituents such as carboxy, anhydride, ester, amide, imide or nitrile on the double bond. Donor monomers have substituents such as alkyl, vinyl, aryl, ether, sulfide and silane. A partial list of donor and acceptor monomers is provided in Table 7.6.65.-... 

The reaction of tetramethylsilane with fluorine led to the isolation of several, partially fluorine-substituted tetramethylsilanes (see Tables VII-IX), and preservation of over 80% of the silicon-carbon bonds in the initial, tetramethylsilane reactant. The stability of many of the partially fluorinated germanes and silanes (some are stable to over 100°C) is very surprising, for the possibility of elimination of hydrogen fluoride is obvious. Indeed, before the first reported synthesis (12) of... 

FIG. 8. (a) The total and partial pressures p and (b) the partial pressure ratio of silane and hydrogen in a silane-hydrogen mixture, at different flow ratios The total flow rate is 30 seem. (Adapted from E. A. G. Hamers. Ph.D. Thesis. Universiteit Utrecht. Utrecht, the Netherlands. 1998. with permission.)... 

To verify the model and to establish in which process parameter space it is valid, a comparison is made with experimental data. These experimental data are the partial pressures of silane, disilane, and hydrogen and the growth rate, obtained during deposition of amorphous silicon. Data are compared for various combinations of the total pressure in the reactor, the electrical power, and the frequency of the power source. 

Pressure variation. In Figure 17 are shown the effects of total pressure on the relative pressures (i.e., the ratio of the partial pressure to the total pressure) of silane, hydrogen, and disilane (Fig. 17a) and on the deposition rate (Fig. 17b). The RF frequency is 50 MHz, and the plasma power is 5 W. The relative pressure of hydrogen slowly increases, and the relative pressure of silane slowly decreases, both in model as well as in experiment. This is caused by an increase in silane depletion at higher total pressures, which results from a higher power dissipation... 

At about 30 Pa, the experimental deposition rate (Fig. 17b) clearly shows a sudden increase, which is not revealed by the model. In addition, the partial pressure of silane decreases (and of hydrogen increases). These features have been observed in other experiments as well [245-248], and are caused by the transition from the a- to the y -regime. 

The partial pressure of disilane as a function of plasma power first increases due to the higher production of silane radicals. Above a certain power the increase in disilane dissociation is higher than the increase in disilane production hence the disilane partial pressure decreases again. Similar behavior has been obserbed by Kae-Nuneet al. [217]. 

The partial pressures of the stable neutral molecules in the discharge (silane, hydrogen, disilane, trisilane) can be measured by a quadrupole mass spectrometer (QMS). The QMS usually is mounted in a differentially pumped chamber, which is connected to the reactor via a small extraction port [286]. In the ASTER system a QMS is mounted on the reactor that is used for intrinsic material deposition. The QMS background pressure (after proper bake-out) is between 10 and 10 mbar. The controllable diameter in the extraction port is adjusted so that during discharge operation the background pressure never exceeds 10"" mbar. 

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