Dynamics of tungsten hexacarbonyl, dicobalt octacarbonyl and their fragments adsorbed on silica surfaces

TL;DR

This study uses first principles molecular dynamics to explore how tungsten and cobalt carbonyl molecules and their fragments behave and vibrate on silica surfaces, providing insights relevant for nanostructure fabrication.

Contribution

It offers new insights into the stability, mobility, and vibrational signatures of precursor molecules on silica surfaces during electron beam induced deposition.

Findings

W(CO)6 and Co2(CO)8 are stable and mobile at room temperature on hydroxylated silica.

Chemisorbed W(CO)5 and Co(CO)4 do not change their binding sites at room temperature.

Vibrational spectra can distinguish different precursor forms on the substrate.

Abstract

Tungsten and cobalt carbonyls adsorbed on a substrate are typical starting points for the electron beam induced deposition of tungsten or cobalt based metallic nanostructures. We employ first principles molecular dynamics simulations to investigate the dynamics and vibrational spectra of W(CO)6 and W(CO)5 as well as Co2(CO)8 and Co(CO)4 precursor molecules on fully and partially hydroxylated silica surfaces. Such surfaces resemble the initial conditions of electron beam induced growth processes. We find that both W(CO)6 and Co2(CO)8 are stable at room temperature and mobile on a silica surface saturated with hydroxyl groups (OH), moving up to half an Angstr\"om per picosecond. In contrast, chemisorbed W(CO)5 or Co(CO)4 ions at room temperature do not change their binding site. These results contribute to gaining fundamental insight into how the molecules behave in the simulated time window of 20ps and our determined vibrational spectra of all species provide signatures for experimentally distinguishing the form in which precursors cover a substrate.