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Article Dans Une Revue Journal of Physical Chemistry B Année : 2006

Water Exclusion at the Nanometer Scale Provides Long-Term Passivation of Silicon (111) Grafted with Alkyl Monolayers

Résumé

This work is a quantitative study of the conditions required for a long-term passivation of the interface silicon−alkyl monolayers prepared by thermal hydrosilyation of neat 1-alkenes on well-defined H−Si(111) surfaces. We present electrochemical capacitance measurements (C−U) in combination with ex situ atomic force microscopy (AFM) observations and X-ray photoelectron spectroscopy (XPS) measurements. Capacitance measurements as a function of the reaction time and XPS data reveal close correlations between the chemical composition at the interface and its electronic properties. A very low density of states is found if suboxide formation is carefully prevented. The monitoring of C−U plots and AFM imaging upon exposure of the sample in diverse conditions indicate that the initial electronic properties and structure of the interface are long-lasting only when the monolayer surface coverage is θ > 0.42. A model demonstrates that this threshold value corresponds to a monolayer with intermolecular channels narrower than ∼2.82 Å, which is equal to the diameter of a water molecule. Water exclusion from the monolayer promotes long-term passivation of the silicon surface against oxidation in air and water as well as perfect corrosion inhibition in 20% NH4F. We provide two criteria to assess when a sample is optimized:  The first one is an effective dielectric constant <2.5, and the second one is a very characteristic energy diagram at open circuit potential.

Domaines

Chimie Matériaux

Dates et versions

hal-04166437 , version 1 (19-07-2023)

Identifiants

Citer

P. Gorostiza, C. Henry de Villeneuve, Q. Sun, F. Sanz, X. Wallart, et al.. Water Exclusion at the Nanometer Scale Provides Long-Term Passivation of Silicon (111) Grafted with Alkyl Monolayers. Journal of Physical Chemistry B, 2006, 110 (11), pp.5576-5585. ⟨10.1021/jp054825c⟩. ⟨hal-04166437⟩
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