Using mechanistic data from surface science studies on electron-induced reactions of organometallic precursors, cis-Pt(CO)2Cl2 (1) was designed specifically for use in focused electron beam induced deposition (FEBID) of Pt nanostructures. Electron induced decomposition of adsorbed 1 under ultrahigh vacuum (UHV) conditions proceeds through initial CO loss as determined by in situ X-ray photoelectron spectroscopy and mass spectrometry. Although the Pt-Cl bonds remain intact during the initial decomposition step, larger electron doses induce removal of the residual chloride through an electron-stimulated desorption process. FEBID structures created from cis-Pt(CO)2Cl2 under steady state deposition conditions in an Auger spectrometer were determined to be PtCl2, free of carbon and oxygen. Coupled with the electron stimulated removal of chlorine demonstrated in the UHV experiments, the Auger deposition data establish a route to FEBID of pure Pt. Results from this study demonstrate that structure-activity relationships can be used to design new precursors specifically for FEBID.

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Toward the goal of better understanding the elementary steps involved in the electron beam-induced deposition (EBID) of organometallic precursors, the present study is aimed at understanding the sequence of electronstimulated reactions of surface-bound η 3 -allyl ruthenium tricarbonyl bromide [(η 3 -C 3 H 5 )Ru(CO) 3 Br], an organometallic complex with three different ligands: carbonyl (CO), halide (Br), and η 3 -allyl (η 3 -C 3 H 5 ). X-ray photoelectron spectroscopy and mass spectrometry were used in situ to probe the effects of 500 eV electrons on nanometer scale films of [(η 3 -C 3 H 5 )Ru-(CO) 3 Br]. Initially, electron irradiation decomposes the precursor, reducing the central Ru atom and causing the ejection of CO ligands into the gas phase. Experimental evidence points to the inability of electron irradiation to remove the carbon atoms of the η 3 -allyl (η 3 -C 3 H 5 ) ligand from the resulting EBID deposits. Although the Br atoms are not labile in the initial molecular decomposition step, they are removed from the film after exposure to higher electron doses as a result of a slower, electron-stimulated desorption process. Comparative studies with [(η 3 -C 3 H 5 )Ru(CO) 3 Cl] reveal that the identity of the halogen does not influence the elementary reaction steps involved in the decomposition process. Collectively, results from these studies suggest that sufficiently volatile organometallic precursors with a small number of carbonyl and halide ligands could be used to generate deposits in EBID with significantly higher metal concentrations (and correspondingly lower levels of organic contamination) compared to existing EBID precursors.

Electron-induced surface reactions of (η-CH)Fe(CO)Mn(CO) were explored in situ under ultra-high vacuum conditions using X-ray photoelectron spectroscopy and mass spectrometry. The initial step involves electron-stimulated decomposition of adsorbed (η-CH)Fe(CO)Mn(CO) molecules, accompanied by the desorption of an average of five CO ligands. A comparison with recent gas phase studies suggests that this precursor decomposition step occurs by a dissociative ionization (DI) process. Further electron irradiation decomposes the residual CO groups and (η-CH, Cp) ligand, in the absence of any ligand desorption. The decomposition of CO ligands leads to Mn oxidation, while electron stimulated Cp decomposition causes all of the associated carbon atoms to be retained in the deposit. The lack of any Fe oxidation is ascribed to either the presence of a protective carbonaceous matrix around the Fe atoms created by the decomposition of the Cp ligand, or to desorption of both CO ligands bound to Fe in the initial decomposition step. The selective oxidation of Mn in the absence of any Fe oxidation suggests that the fate of metal atoms in mixed-metal precursors for focused electron beam induced deposition (FEBID) will be sensitive to the nature and number of ligands in the immediate coordination sphere. In related studies, the composition of deposits created from (η-CH)Fe(CO)Mn(CO) under steady state deposition conditions, representative of those used to create nanostructures in electron microscopes, were measured and found to be qualitatively consistent with predictions from the UHV surface science studies.