Interaction of W(CO)$_6$ with SiO$_2$ Surfaces -- A Density Functional Study

TL;DR

This study uses density functional theory to explore how W(CO)$_6$ molecules interact with different SiO$_2$ surfaces, revealing weak physisorption on fully hydroxylated surfaces and dissociation on partially hydroxylated ones, informing nano-deposit growth.

Contribution

It provides detailed computational insights into the molecular interactions and dissociation mechanisms of W(CO)$_6$ on hydroxylated SiO$_2$ surfaces, highlighting the effects of surface hydroxylation.

Findings

Weak physisorption on fully hydroxylated SiO$_2$

Spontaneous dissociation on partially hydroxylated SiO$_2$

Preference for binding multiple CO ligands

Abstract

The interaction of tungsten hexacarbonyl W(CO)$_6$ precursor molecules with SiO$_2$ substrates is investigated by means of density functional theory calculations with and without inclusion of long range van der Waals interactions. We consider two different surface models, a fully hydroxylated and a partially hydroxylated SiO$_2$ surface, corresponding to substrates under different experimental conditions. For the fully hydroxylated surface we observe only a weak interaction between the precursor molecule and the substrate with physisorption of W(CO)$_6$. Inclusion of van der Waals corrections results in a stabilization of the molecules on this surface, but does not lead to significant changes in the chemical bonding. In contrast, we find a spontaneous dissociation of the precursor molecule on the partially hydroxylated SiO$_2$ surface where chemisorption of a W(CO)$_5$ fragment is observed upon removal of one of the CO ligands from the precursor molecule. Irrespective of the hydroxylation, the precursor molecule prefers binding of more than one of its CO ligands. In the light of these results, implications for the initial growth stage of tungsten nano-deposits on SiO$_2$ in an electron beam induced deposition process are discussed.