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

• Published in: Journal of physical chemistry. C Vol. 124; no. 19; pp. 10593 - 10604
• Main Authors: Thorman, Rachel M, Jensen, Pernille A, Yu, Jo-Chi, Matsuda, Scott J, McElwee-White, Lisa, Ingólfsson, Oddur, Fairbrother, D. Howard
• Format: Journal Article
• Language: English
• Published: American Chemical Society 14.05.2020
• Subjects: bromination; carbon; desorption; energy; gold; ionization; irradiation; ligands; oxygen; spectrometers
• ISSN: 1932-7447; 1932-7455; 1932-7455
• DOI: 10.1021/acs.jpcc.0c01801

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)4I2 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)4I2 predominantly results in the loss of two CO ligands, while dissociative ionization (DI) of Ru­(CO)4I2 leads to significantly more extensive fragmentation. Surface science studies of thin films of Ru­(CO)4I2 adsorbed on gold at −100 °C and irradiated with 500 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)4I2 and its brominated analogue, Ru­(CO)4Br2, produced deposits with a ruthenium-to-halide ratio of ≈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)2I2 species, which is then subject to CO desorption under further electron irradiation, findings likely generalizable to other Ru­(CO)4X2 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.