A simple method to study gas phase reactions

Abstract

To understand better the impact of gas phase reactions on chemical vapor deposition, a new experimental method has been developed to isolate and study homogeneous reactions separately from heterogeneous reactions. This new system heats reactant gases by rapidly compressing them to temperatures greater than 1,000 K; the walls of the reactor remain constant at 500 K or less. Pressure and volume measurements determine the mean temperature of the gas. Results from a series of test reactions and simple models show that this apparatus and measurement method work well. The apparatus is inexpensive and simple to use, and has advantages over shock tubes and static systems.

Silane pyrolysis in a piston reactor

“…Note that the peak T,,, is roughly the same in both experiments. Morrison and Reimer (1987) have shown that the sharpness of the peak T, is largely due to the rebound of the piston (expansion cooling). Figure 3 shows the conversion as a function of peak T,,, for 1% mixtures of SiH, in Ar and He.…”

“…A previous manuscript describes the reactor in detail (Morrison and Reimer, 1987), and we only review the principles here ( inside diameter of 10 cm; a substrate or window closes one end of the cylinder. A piston and rod assembly slides inside the cylinder forming a gas tight seal; a Teflon coating on the interior cylinder surface lubricates the piston seals.…”

“…The piston reactor (Morrison and Reimer, 1987) avoids many of these problems. The concept is very simple: a piston in a cylinder compresses a mixture of 1% SiH, in noble gas to high temperatures (-1,000 K) until the SiH, decomposes; the cylinder walls remain at a low temperature (-500 K) because of their large heat capacity.…”

“…and 0 -1% SiH, + 10% H,. byMorrison and Reimer (1987). To review, this method requires integrating the equation dT/dt = Hydrogen to silicon ratio (H/Si) for silicon soot particles.…”