Kinetics of laser thermal decomposition of trimethylamine alane

Using a focused Ar ion laser emitting at 514 nm, aluminum dots have been deposited on silicon-coated quartz substrate via a pyrolytic decomposition of trimethylamine alane. The growth kinetics of these Al dots was investigated as a function of the precursor pressure (1 to 7.5 mbar) and the laser-induced temperature. The threshold temperature for the onset of growth was observed to be 210°C. Deposition rates as high as 3 μm/s have been obtained at temperatures of about 300°C and were found to be independent of the precursor partial pressure. The activation energy of the deposition process was determined to be 18 kcal/mol. In order to understand the growth mechanism of these dots, several elementary steps occurring at the aluminum surface have been assumed involving AlH3 as well as AlH2 and AlH adspecies. From this study it is concluded that the desorption of the hydrogen molecules is the rate-limiting step in the laser chemical vapor deposition of Al from trimethylamine alane.