Homogeneous thermal decomposition of dimethylzinc in a metal–organic vapour phase epitaxy reactor

Abstract

The homogeneous thermal decomposition of dimethylzinc (DMZn) in a low-pressure metal–organic vapour phase epitaxy (LP MOVPE) reactor has been investigated as a function of both temperature and reactor pressure in both H₂ and He carrier gases, using ex situ FTIR absorption spectroscopy. The decomposition behaviour for pyrolysis in He at atmospheric pressure is similar to that found previously for pyrolysis in a toluene (a radical scavenger) carrier; DMZn decomposes predominantly by homolytic fission in He although we believe radical attack on DMZn is responsible for the small amount of methane which is produced. The rate of pyrolysis of DMZn, at atmospheric pressure, is enhanced in an H₂ carrier, where the only detectable product is methane. The enhanced pyrolysis in H₂ is attributed to radical attack by H˙ on DMZn. Studies of DMZn pyrolysis in H₂ as a function of pressure, between atmospheric pressure and 76 Torr, indicated only a small effect on the overall pyrolysis characteristics. The reaction goes essentially to completion at all the pressures investigated with no significant difference in the temperature required to achieve total decompostion of the DMZn.