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

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 Co ₂(CO)₈ are stable at room temperature and mobile on a silica surface saturated with hydroxyl groups (OH), moving up to half an Angström 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 20 ps and our determined vibrational spectra of all species provide signatures for experimentally distinguishing the form in which precursors cover a substrate.