THERMAL-STABILITY OF METHYL-GROUPS ON SI(100) GENERATED BY THE DECOMPOSITION OF TETRAMETHYLGERMANE

The adsorption and thermal decomposition of tetramethylgermane on Si(100) have been studied by ultraviolet photoelectron spectroscopy, static secondary ion mass spectrometry, temperature-programmed desorption, and Auger electron spectroscopy. Tetramethylgermane adsorbs molecularly on Si(100) at 110 K. In temperature-programmed desorption experiments, most of the tetramethylgermane reversibly desorbs at 141 +/- 4 K. The remaining tetramethylgermane decompose at higher surface temperatures by breaking of a C-Ge bond resulting in the formation of a methyl group and Ge(CH3)3, the latter evolving into the gas phase. Further heating causes decomposition of the methyl group. The hydrogen atoms released by methyl group decomposition form surface Si monohydrides, which later combine to desorb molecular H-2. The methyl groups decompose with a pseudo-first-order preexponential of (1 +/- 5) x 10(8) s-1 and an activation energy of 29 +/- 1 kcal mol-1.