Bond-specific reaction kinetics during the oxidation of (111) Si: Effect of n-type doping

TL;DR

This study investigates how free carriers, specifically electrons, influence the oxidation reaction kinetics of silicon (111) surfaces, revealing bond-specific effects and the stabilization of oxide thickness.

Contribution

It provides real-time, bond-specific insights into how electrons affect silicon oxidation chemistry, a novel approach in understanding doping effects.

Findings

Electrons increase reactivity of Si-Si back bonds.

Natural oxide thickness stabilizes near 1 nm regardless of kinetics.

Bond-specific differences in oxidation behavior are observed.

Abstract

It is known that a higher concentration of free carriers leads to a higher oxide growth rate in the thermal oxidation of silicon. However, the role of electrons and holes in oxidation chemistry is not clear. Here, we report real-time second-harmonic-generation data on the oxidation of H-terminated (111)Si that reveal that high concentrations of electrons increase the chemical reactivity of the outer-layer Si-Si back bonds relative to the Si-H up bonds. However, the thicknesses of the natural oxides of all samples stabilize near 1 nm at room temperature, regardless of the chemical kinetics of the different bonds.