Oxidation of Atomically Flat and Hydrogen-Terminated Si(111) Surfaces by Hydrogen Peroxide

Abstract

The electrochemical current-voltage curve of a Si͑111͒ surface measured in an aqueous solution is very sensitive to the surface condition. Using this property, we analyzed the Si͑111͒ surface after chemical oxidation by H 2 O 2 . Thermodynamically, Si-Si back bonds of surface Si-H bonds are oxidized more easily than the Si-H bonds. However, when the surface was atomically fattened and hydrogen-terminated, the oxidation rate of the Si-Si back bonds was lowered and the surface Si-H bonds and Si-Si back bonds were oxidized simultaneously. The lowered reactivity of the Si-Si back bonds was attributed to the hindrance of the approach of H 2 O 2 molecules to the Si-Si back bonds by the Si-H bonds regularly stretching perpendicular to the surface. Fourier transform infrared ͑FTIR͒ spectra showed that the Si-Si back bonds on step sites were oxidized very easily, and this was attributed to easy access of H 2 O 2 molecules to the Si-Si bonds on the step sites. These results indicate that the regular structure of the atomically flattened Si͑111͒ surface is the reason for its good stability against chemicals.

Measurement and Control of In-Plane Surface Chemistry During Oxidation of H-Terminated (111)Si

“…Some reports suggest that oxidation does not initiate at step sides (9). However, FTIR data indicate that steps facilitate oxidation (10). Our data elucidate the crucial role of steps.…”

Etching Silicon with HF-H2O2-Based Mixtures: Reactivity Studies and Surface Investigations

“…In general, chemical Si surface oxidation with H 2 O 2 and without HF is analogous to the Si surface passivation in electrochemical etching without HF, where the anodic potential generates holes. 46 Si oxidation with H 2 O 2 occurs preferentially at the surface near Si−Si bonds (also called Si back bonds). The Si−H bonds remain intact because they are kinetically inert.…”

Enhanced room temperature oxidation in silicon and porous silicon under 10 keV x-ray irradiation

“…Si-H bonds are known to stretch perpendicular to the silicon surface and hinder the approach of oxidizing species. 17 To further explore the role of surface hydrogen termination, we irradiated porous silicon samples that contained a lower SiH x content. These samples were prepared by exposing porous silicon to 1.5 mM KOH ͑1:5 of 9 mM aqueous KOH and ethanol͒ for 10 min.…”

“…Thus, we can conclude that surface hydrogen species play an important and significant role in determining the rate of radiation-enhanced oxidation that is consistent with other oxidation reports. 11,17 Further, due to the greater abundance of surface hydrogen species on freshly anodized PSi samples, it is not surprising that the rate of radiation-enhanced oxidation is less for porous silicon compared to silicon wafers.…”