Competition of silene/silylene chemistry with free radical chain reactions using 1-methylsilacyclobutane in the hot-wire chemical vapor deposition process

摘要

The gas-phase reaction chemistry of using1-methylsilacyclobutane (MSCB) in the hot-wire chemical vapordeposition (CVD) process has been investigated by studyingthe decomposition of MSCB on a heated tungsten filament andsubsequent gas-phase reactions in a reactor. Three pathwaysexist to decompose MSCB on the filament to form ethene/methylsilene, propene/methylsilylene, and methyl radicals. Theactivation energies for forming propene and methyl radical,respectively, are determined to be 68.7 ± 1.3 and 46.7 ±2.5 kJ·mol−1, which demonstrates the catalytic nature of thedecomposition. The secondary gas-phase reactions in thehot-wire CVD reactor are characterized by the competitionbetween a free radical chain reaction and the cycloaddition of silene reactive species produced either from the primarydecomposition of MSCB on the filament or the isomerization of silylene species. At lower filament temperatures of 1000−1100 °Cand short reaction time (t ≤ 15 min), the free radical chain reaction is equally important as the silene chemistry. With increasingfilament temperature and reaction time, silene chemistry predominates