Electron-Induced Reactions of Ru(CO)4I2: Gas Phase, Surface, and Electron Beam-Induced Deposition

The reactions of low energy (<100 eV) electrons with organometallic precursors underpin the fabrication of metal-containing nanostructures using focused electron beam-induced deposition. To understand these reactions at a molecular level, we have studied the electron-induced reactions of Ru(CO)(4)I-2 in three different environments: as isolated molecules in the gas phase, adsorbed as thin films on surfaces, and as used in electron beam-induced deposition (EBID) in an Auger spectrometer. Gas-phase studies show that dissociative electron attachment (DEA) to Ru(CO)(4)I-2 predominantly results in the loss of two CO ligands, while dissociative ionization (DI) of Ru(CO)(4)I-2 leads to significantly more extensive fragmentation. Surface science studies of thin films of Ru(CO)(4)I-2 adsorbed on gold at -100 degrees C and irradiated with S00 eV electrons show that decomposition proceeds in two distinct steps: (1) an initial loss of two CO ligands, followed by (2) a slower step, where the residual two CO ligands desorb, leaving RuI2 on the surface. EBID using Ru(CO)(4)I-2 and its brominated analogue, Ru(CO)(4)Br-2, produced deposits with a ruthenium-to-halide ratio of approximate to 1:2 and minimal carbon and oxygen contamination. These results suggest that DEA is dominant over DI in the initial deposition step on the surface. This step produces a partially decarbonylated Ru(CO)(2)I-2 species, which is then subject to CO desorption under further electron irradiation, findings likely generalizable to other Ru(CO)(4)X-2 species (X = halide). The desorption of CO from the partially decarbonylated intermediate differs markedly from the results obtained for other metal carbonyls (e.g., W(CO)(6)), a difference tentatively ascribed to the presence of M- X bonds.