Vapor phase decomposition

Equation 11 predominates in uncatalyzed vapor-phase decomposition and photo-chemicaHy initiated reactions. In catalytic reactions, and especially in solution, the nature of the reactants determines which reaction is predominant. 

The term direct TXRF refers to surface impurity analysis with no surface preparation, as described above, achieving detection Umits of 10 °—10 cm for heavy-metal atoms on the silicon surface. The increasit complexity of integrated circuits fabricated from silicon wafers will demand even greater surfrce purity in the future, with accordingly better detection limits in analytical techniques. Detection limits of less than 10 cm can be achieved, for example, for Fe, using a preconcentration technique known as Vapor Phase Decomposition (VPD). 

Figures Schematic arrangement for vapor phase decomposition iVPD) appiied to siiicon wafers.

VPD-AAS Vapor Phase Decomposition-Atomic Absorption Spearoscopy... 

Vapor-phase decomposition and collection (Figs 4.16 to 4.18) is a standardized method of silicon wafer surface analysis [4.11]. The native oxide on wafer surfaces readily reacts with isothermally distilled HF vapor and forms small droplets on the hydrophobic wafer surface at room temperature [4.66]. These small droplets can be collected with a scanning droplet. The scanned, accumulated droplets finally contain all dissolved contamination in the scanning droplet. It must be dried on a concentrated spot (diameter approximately 150 pm) and measured against the blank droplet residue of the scanning solution [4.67-4.69]. VPD-TXRF has been carefully evaluated against standardized surface analytical methods. The user is advised to use reliable reference materials [4.70-4.72]. 

Carbon tetrachloride was also found to react with pyrryl potassium to give 3-chloropyridine, however the mechanism is obscure and would justify further investigation. In a preparatively useful reaction, pyrrole and chloroform in the vapor phase at 500-550° gave 3-chloro-pyridine (33%) and a little 2-chloropyridine (2-5%). No interconversion of the isomers occurred under these conditions, though pyrolytic rearrangement of N-alkylpyrrole to 3-substituted pyridines is considered to involve 2-alkylpyrroles as intermediates. There is some independent evidence that dichlorocarbene is formed in the vapor phase decomposition of chloroform. ... 

Consider possible vapor-phase reactions. These might include combustion reactions, other vapor-phase reactions such as the reaction of organic vapors with a chlorine atmosphere, and vapor-phase decomposition of materials such as ethylene oxide or organic peroxide. 

The tabulated data have been obtained for the vapor phase decomposition of ethylene oxide (A) into methane and carbon monoxide at 414.5°C (Heppert Mack, JACS 5J 2706, 1929). Show that the rate equation is first order, nt = 2na0-na... 

The vapor phase decomposition of phosphine is irreversible first order and is in accord with the stoichiometry,... 

The heat for Reaction (4.49) is 88 kcal/mol, and for Reaction (4.50) it is about 50 kcal/mol. The latter reaction predominates in uncatalyzed vapor-phase decomposition and photochemically initiated reactions. 

The formation of sulfur monoxide in the vapor phase decomposition of ethylene episulfoxide was recently confirmed by microwave spectroscopy. The rotational lines of SO in the electronic ground state were observed ... 

Another reaction involving free radicals is the vapor-phase decomposition of acetaldehyde ... 

Derivation The ore is converted to a cyanonitride and is chlorinated to obtain zirconium tetrachloride. This is reduced with magnesium (Kroll process) in inert atmosphere. The metal can be prepared in a highly pure and ductile form by vapor-phase decomposition of the tetraiodide. Hafnium must be removed for uses in nuclear reactors... 

Example 2-6 The interpretation of kinetic data for gaseous reactions is similar to that for liquid systems. The analysis for a reversible case is well illustrated by the vapor-phase decomposition of hydrogen iodide,... 

Vapor Phase Decomposition of Aromatic Hydrocarbons by Electric Discharge... 

Passage of ethanol vapors over pyro-phosphoric acid at a temperature of 250° to 300° C. results in a 90 per cent yield of ethylene 99.6 per cent pure, no ether and 0.4 per cent of an impurity, possibly a saturated hydrocarbon.51 Such catalysts exert a powerful polymerizing action on olefins and short times of contact must be used to prevent secondary decompositions. At temperatures of about 150° C. sulfuric acid gives only low conversions to ethylene. Such catalysts as the phosphoric acids aud sulfuric acid when used on inert supports for the vapor phase decomposition of alcohols are much more difficult to control in their actions than when... 

The vapor-phase decomposition of methyl-/-butyl ether (MTBE) into methanol and isobutene was examined in a shell- and tube-type catalytic membrane reactor by Choi and... 

Kuhn and DeAngelis (1954) looked at the thermal decomposition of vicinal dinitrites. The vapor-phase decompositions of propane-1,2-dinitrite, butane-2,3-dinitrite, and cis- and rra s-cyclohexane-1,2-dinitrite all proceed via the overall reaction... 

After calcinations and reductions in flowing hydrogen at 450° the resulting catalysts were used in the vapor phase decomposition of alcohols. It was calculated that the Cu-catalysts received in such a way contained 19 atomic layers and the Ni catalyst 160-240 atomic layers. 

Vapor phase decomposition (VPD) is a special preparation technique that is used for the measurement of surface contaminations on wafers (strictly speaking, the average concentration in its oxide or nitride coating)... 

FIGURE 40.1 Principle of vapor phase decomposition (VPD). Adapted from Reference [17]. 

---