Interaction of W(CO)${}_{6}$ with SiO${}_{2}$ surfaces: A density functional study

Interaction of W(CO) $_{6}$ with SiO $_{2}$ surfaces: A density functional study

Kaliappan Muthukumar, Ingo Opahle, Juan Shen, Harald O. Jeschke, and Roser Valentí

Phys. Rev. B 84, 205442 – Published 21 November 2011

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 light of these results, implications for the initial growth stage of tungsten nanodeposits on SiO $_{2}$ in an electron-beam-induced deposition process are discussed.