RESUMO
The tungsten carbonyl dimethyldithiolene (dmdt) complexes W(CO)4(dmdt), W(CO)2(dmdt)2, and W(dmdt)3 were evaluated as potential single-source precursors for the chemical vapor deposition of WS2. The results of TGA-MS, DIP-MS, and pyrolysis with NMR analysis were consistent with a thermal decomposition pathway in which loss of 2-butyne through a retro[3+2]cycloaddition of the dithiolene ligand generated terminal sulfido ligands. Aerosol-assisted chemical vapor deposition onto silicon substrates was performed using all three complexes, yielding 2H-WS2 thin films as characterized by Raman spectroscopy and GI-XRD. Film morphology and elemental composition of the films were determined using SEM, EDS, and XPS. Four-point probe measurements afforded a film resistivity of 8.37 Ωcm for a sample deposited from W(dmdt)3 in toluene at 600 °C.
RESUMO
Aerosol-assisted chemical vapor deposition of MoS2 from solutions containing the single-source precursors cis-Mo(CO)4(TMTU)2 and Mo(CO)5(TMTU) in toluene was compared to depositions from the coreactant solution containing Mo(CO)6 and uncoordinated TMTU in toluene. The results were used to assess the significance of ligand precoordination on the properties of the deposited films. Raman spectra and GI-XRD patterns of the films show that the single-source precursors produced more intense and sharper signals for 2H-MoS2 as compared to the coreactant system of Mo(CO)6 and TMTU, which is indicative of improved crystallinity. SEM and XPS were also used to assess morphology and film composition. Thermolysis of cis-Mo(CO)4(TMTU)2 and analysis of the pyrolysis products by GC-MS and 1H NMR suggested a decomposition mechanism of the TMTU ligand where a terminal sulfido is generated on the molybdenum center with loss of a heteroatom stabilized carbene.