Mass-spectrometric study of thermal decomposition of diethylzinc and diethyltellurium

Abstract

A mass-spectrometric study of the thermal decomposition of Group II and VI alkyls involved in ZnTe growth by metal-organic chemical vapour deposition (MOCVD) is reported. The pyrolysis of diethylzinc (Et₂Zn) and diethyltellurium (Et₂Te) alone and together were followed with the change of the inlet partial pressure ratio (R= Te/Zn = 1 and 5). Under He and H₂, the thermal decomposition of Et₂Zn organometallic species leads to the formation of n-C₄H₁₀, C₂H₄ and C₂H₆. The pyrolysis of Et₂Te produces ethene in excess of other hydrocarbons. For co-decomposition in an He atmosphere, pyrolysis curves as a function of temperature, with R= 1 show that the temperature corresponding to the half-decomposition ratio (T₅₀) of Et₂Te is lowered by 25 °C relative to that of Et₂Te alone. For R= 5, the T₅₀ of Et₂Zn is increased by 30 °C relative to that of the precursor alone. The kinetics of decomposition of Et₂Zn and Et₂Te alone showed no thermal hysteresis, whereas a strong hysteresis loop between heating and cooling of the susceptor was recorded during the co-decomposition. The dependence of these effects on R and temperature are discussed in relation to surface reactions.