HOMOGENEOUS THERMAL-DECOMPOSITION OF DIMETHYLZINC IN A METAL-ORGANIC VAPOR-PHASE EPITAXY REACTOR - AN EX-SITU INVESTIGATION BY FTIR ABSORPTION-SPECTROSCOPY

The homogeneous thermal decomposition of dimethylzinc (DMZn) in a low- pressure metal-organic vapour phase epitaxy (LP MOVPE) reactor has bee n investigated as a function of both temperature and reactor pressure in both H-2 and He carrier gases, using ex situ FTIR absorption spectr oscopy. The decomposition behaviour for pyrolysis in He at atmospheric pressure is similar to that found previously for pyrolysis in a tolue ne (a radical scavenger) carrier; DMZn decomposes predominantly by hom olytic fission in He although we believe radical attack on DMZn is res ponsible for the small amount of methane which is produced. The rate o f pyrolysis of DMZn, at atmospheric pressure, is enhanced in an H-2 ca rrier, where the only detectable product is methane. The enhanced pyro lysis in H-2 is attributed to radical attack by H on DMZn. Studies of DMZn pyrolysis in H-2 as a function of pressure, between atmospheric pressure and 76 Torr, indicated only a small effect on the overall pyr olysis characteristics. The reaction goes essentially to completion at all the pressures investigated with no significant difference in the temperature required to achieve total decomposition of the DMZn.