MECHANISTIC STUDIES OF THE THERMAL-DECOMPOSITION OF METAL-CARBONYLS ON NI(100) SURFACES IN CONNECTION WITH CHEMICAL-VAPOR-DEPOSITION PROCESSES

The thermal decomposition of Fe(CO)(5), Cr(CO)(6), Mo(CO)(6), and W(CO )(6) on Ni(100) surfaces and under ultrahigh vacuum conditions was stu died by using temperature programmed desorption and x-ray photoelectro n spectroscopies. The initial adsorption of those metal carbonyls is m ostly molecular at low temperatures, but complete decarbonylation to t he naked metal takes place in all cases upon thermal activation. Exper iments with coadsorbed isotopically labeled (CO)-C-13 provided indirec t evidence for a stepwise mechanism for Fe(CO)(5) which may include th e formation of tetra- and tricarbonyl intermediates on the surface. Fo r Cr(CO)(6), Mo(CO)(6), and W(CO)(6), on the other hand, complete deco mposition occurs in a narrow range of temperature, and no intermediate could be isolated on the surface. The deposition of metal films via m etal carbonyl activation was studied under steady state conditions as well. Continuous deposition was seen at substrate temperatures as low as 300 K, but the grown films were found to incorporate both carbon an d oxygen under most conditions tested and to change their morphology d epending on the substrate temperature during deposition. (C) 1996 Amer ican Vacuum Society.