Study of homogeneous thermal decomposition of triethylgallium, triethylaluminum with ammonia and tungsten dimethylhydrazido complex using in situ Raman spectroscopy and computational chemistry

The gas phase thermal decomposition pathways for the metal-organic precursor of TEGa ((C2H5)3Ga, Triethylgallium) were followed using in situ Raman spectroscopy in an up-flow, cold-wall CVD (Chemical Vapor Deposition) reactor. Raman shift located at 490cm-1, 517cm-1, 537cm-1 , and 555cm-1 were assigned to the vibrational frequencies between gallium and the α–carbon of (Et)3Ga, (DEGa) 2, (Et)GaH–Ga(Et)2 and (Et)GaH–GaH2, respectively.DFT (Density Functional Theory) calculations were in good agreement with experimental observations. Identification of intermediates by Raman spectroscopy confirmed that both β–hydride elimination and homolysis homogeneous thermal decomposition reactions occur under the reactor conditions. The mass transport simulation using the finite element method supports the presence of both reactions. In addition to the peak assignments, DFT calculations using the B3LYP/LanL2DZ (Becke, three-parameter, Lee-Yang-Par/Los Alamos National Laboratory 2-Double-Zeta) model chemistry were performed to screen 17 envisioned routes from 34 reactions.;Homogeneous thermal decomposition pathways for triethylaluminum ((C 2H5)3Al; TEAl) were investigated. Raman scattering experiments were performed on TEAl neat and in the presence of ammonia in the reactor.Raman shifts were observed for the decomposition products TEAl:NH 3, DEAlH, TEAl:NH3 TS, H2N-AlH-NH-AlH2, H2Al-NH2, MEAlH2, MEAlH-AlH2 and DEAl-AlH2. DFT calculations using the B3LYP/LanL2DZ level of theory were carried out to optimize the geometry of each intermediate and likely transition structures to estimate activation energies.;The gas-phase decomposition pathways of the tungsten dimethylhydrazido complexes Cl4(RCN)W(NNMe2) (1a: R=CH 3;1b: R=Ph), precursors for single source deposition of WNxCy, were investigated using a combination of Raman scattering experiments and DFT calculations. DFT calculations (B3LYP/LanL2DZ) were used to estimate Raman active frequencies and explore the reaction surface. Dimethylamine and methylmethyleneimine, products from N-N cleavage of the hydrazido ligand, were observed under deposition conditions and identified by comparison with previously reported Raman shifts and calculated frequencies.Combining experimental thermal decomposition studies by Raman spectroscopy with DFT calculations and FEM (Finite Element Method) reactor modeling is a powerful approach for quantitative CVD kinetics analysis.