Surface Reactions of Low-Energy Argon Ions with Organometallic Precursors

Abstract

A combination of in situ X-ray photoelectron spectroscopy and mass spectrometry has been used to elucidate the elementary surface reactions initiated by the interaction of low-energy (860 eV) argon ions with three organometallic precursors [Ru­(CO)4I2, Co­(CO)3NO, and WN­(NMe2)3]. The effects of ion exposure on each precursor can be described by a largely sequential series of surface reactions. The initial step involves ion-induced decomposition of the precursor to create a nonvolatile deposit, followed by physical sputtering of the atoms in the deposit. For the precursors that contain CO ligands [Ru­(CO)4I2 and Co­(CO)3NO], ion-induced decomposition is accompanied by desorption of the majority of the CO groups. This is in marked contrast to previous studies of low-energy electron-induced reactions with the same precursors where precursor decomposition yielded only partial desorption of the CO ligands. Conversely, argon ion bombardment of WN­(NMe2)3 led to decomposition without ligand loss. For all three precursors, the initial ion-induced decomposition step was not accompanied by significant desorption of intact precursor molecules, while during subsequent physical sputtering of the deposited atoms, ligand-derived organic and inorganic contaminants were removed at higher rates than the metals. This indicates that controlled ion beam deposition conditions could be used to produce deposits with high metal contents from all three precursors. Comparison of low-energy electron-induced reactions of these three precursors with results of this investigation indicates that secondary electrons do not play an important role in the deposition process, but rather precursor decomposition occurs via efficient ion–molecule energy transfer. These reactions are discussed in the context of focused ion beam-induced deposition.

Low Energy Electron- and Ion-Induced Surface Reactions of Fe(CO)5 Thin Films

“…It is also worth noting that in common with two recent studies where we have investigated low energy ion reactions with adsorbed organometallic precursors, , the significant chemical transformations to Fe­(CO) 5 observed in the form of CO desorption and decomposition, occur in the absence of any measurable molecular desorption, despite the fact that the Fe­(CO) 5 molecules are only bound to the substrate through comparatively weak physisorption interactions. Experimentally, the absence of ion-induced Fe­(CO) 5 desorption is evident in Figure by the absence of a decrease in the Fe XPS signal during the initial stages of Ar + bombardment when Fe­(CO) 5 molecules are undergoing ion-induced decomposition.…”

Charged Particle-Induced Surface Reactions of Organometallic Complexes as a Guide to Precursor Design for Electron- and Ion-Induced Deposition of Nanostructures

“…The data in Figure 6b were fit to a kinetic model that supports this sequential series of surface reactions, providing a rationale for the clearly visible delay in the onset of Ru loss observed experimentally. 88 The calculated cross sections indicate that the rate of the initial ion-induced decomposition of iodide complex 10 leading to CO loss is about five times faster than the physical sputtering of I from RuI 2 , which in turn is itself about five times faster than the rate of Ru sputtering. This sequence of reaction steps indicates that production of pure Ru deposits could be achieved under tailored deposition conditions.…”

“…Indeed, the variation in the coverage of Ru, CO and I as a function of Ar + dose can be described by a sequential series of reactions where initial ion-induced precursor decomposition (eq ) is followed by preferential Ar + sputtering of iodine (eq ) followed by ruthenium (eq ). The data in Figure b were fit to a kinetic model that supports this sequential series of surface reactions, providing a rationale for the clearly visible delay in the onset of Ru loss observed experimentally . The calculated cross sections indicate that the rate of the initial ion-induced decomposition of iodide complex 10 leading to CO loss is about five times faster than the physical sputtering of I from RuI 2 , which in turn is itself about five times faster than the rate of Ru sputtering.…”

“…(b) Change in fractional coverage of O, I, and Ru atoms as a function of increasing Ar + dose. The solid fits through the data are generated from the kinetic model described in the text . Reproduced with permission from ref .…”

“…The solid fits through the data are generated from the kinetic model described in the text . Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”