Spontaneous Dissociation of Co2(CO)8 and Autocatalytic growth of Co on SiO2 : A Combined Experimental and Theoretical Investigation

TL;DR

This study combines experimental and theoretical approaches to investigate how pre-treatments of SiO2 surfaces influence the spontaneous dissociation of Co2(CO)8 and the autocatalytic growth of cobalt, revealing the role of surface hydroxyl groups.

Contribution

It provides new insights into the surface chemistry and dissociation mechanisms of Co2(CO)8 on SiO2, highlighting the impact of surface passivation and pre-treatment methods.

Findings

Spontaneous dissociation of Co2(CO)8 occurs on pre-treated SiO2 surfaces.

Surface hydroxylation level controls precursor dissociation and cobalt growth.

Theoretical calculations support the experimental observations of physisorption and chemisorption.

Abstract

We present experimental results and theoretical simulations of the adsorption behavior of the metal-organic precursor Co2(CO)8 on SiO2 surfaces after application of two different pre-treatment steps, namely by air plasma cleaning or a focused electron beam pre-irradiation. We observe a spontaneous dissociation of the precursor molecules as well as auto-deposition of cobalt on the pre-treated SiO2 surfaces. We also find that the differences in metal content and relative stability of these deposits depend on the pre-treatment conditions of the substrate. Transport measurements of these deposits are also presented. We are led to assume that the degree of passivation of the SiO2 surface by hydroxyl groups is an important controlling factor in the dissociation process. Our calculations of various slab settings using dispersion corrected density functional theory support this assumption. We observe physisorption of the precursor molecule on a fully hydroxylated SiO2 surface (untreated surface) and chemisorption on a partially hydroxylated SiO2 surface (pre-treated surface) with a spontaneous dissociation of the precursor molecule. In view of these calculations, we discuss the origin of this dissociation and the subsequent autocatalysis.