Production of Gallium Atoms by Excimer Laser Photolysis of Trimethyl Gallium

摘要

The gas phase kinetics of group III elements such as gallium are important in possible chemically driven energy transfer lasers and in chemical vapor deposition processes in the electronics industry. Excimer laser photodissociation of volatile gallium compounds via multiple photon process provides, in principle, a convenient room temperature source of gallium atoms for study using laser photolysis-laser induced fluorescence techniques. In this paper, we report preliminary results of the multiple photon dissociation of trimethyl gallium at 193 nm. Prompt emission from a number of excited gallium states (5 exp 2 S, 4 exp 2 D, 6 exp 2 S, 6 exp 2 P exp 0 , 5 exp 2 D, and 4 exp 4 P) has been observed. The time histories of the ground state (4 exp 2 P exp 0 /sub 1/2/) and the metastable (4 exp 2 P exp 0 /sub 3/2/) have been measured using laser induced fluorescence. The resulting time profiles are complicated even in the absence of a reactant gas by the apparent production of ground state gallium at relatively long times (approx. 10 mu s) after the excimer laser pulse. Possible mechanisms for this (i.e., radical reactions to produce gallium, energy transfer cascading from high lying metastable states, ionic processes, etc.) are being investigated. These results indicate that the photodissociation of trimethyl gallium at 193 nm is complex. Photolysis studies at other wavelengths and with other precursors are in progress to find a cleaner source of gas phase atomic gallium for kinetic studies. 20 refs., 7 figs. (ERA citation 10:028237)