DECOMPOSITION, OXIDATION, AND HYDROLYSIS KINETICS OF MONOBUTYLTINTRICHLORIDE

摘要

Using a continuously stirred tank reactor (CSTR) system equipped with an in-situ FTIR spectrometer the deposition of tin oxide from monobutyltin trichloride (MBTC) and O_2/H_2O was studied. The overall activation energy measured in the CSTR experiments for pyrolysis of MBTC is 126 kJ/mol, which is considerably lower than predicted by ab initio calculations, 289 kJ/mol. This is attributed to radical attack on MBTC subsequent to the initiation step, which accelerates the decomposition. Deposition of tin oxide from MBTC and oxygen mixtures is observed to occur at temperatures as low as 673 K, well below the temperature at which MBTC begins to decompose. Since direct gas-phase reaction between MBTC and oxygen is not expected, this experimental result is an indication that deposition occurs via surface reactions at these low temperatures (< 723 K). Adding water to the precursor mixture increases the growth rate dramatically. Although ab-initio and equilibrium calculations show that water easily reacts with tin-intermediates such as SnCl_2 or SnCl_3, computational modelling of the CSTR indicates that these reactions do not lead to higher conversion rates of MBTC. Another possibility is that H_2O forms OH sites on the surface, which can easily abstract Cl from the eventual film precursor or even MBTC.