Photoreactivity of Si(111)−H in Ambient

Bodlaki, D.; Borguet, Eric

doi:10.1021/jp0639546

Cited by 9 publications

(5 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Table summarizes the water contact angle values (θ water ) of Si(111) substrates with various surface functionalization (Scheme ). Beginning with the NH 4 F etched Si(111), the atomically flat Si(111)–H results in a hydrophobic surface shown by a large water contact angle (99 ± 6°). , Subsequently, the silicon is slowly oxidized to yield a hydrophilic Si–O x layer on the surface, resulting in the decrease of the contact angle (θ water ≈ 56.2 ± 1.7°). As shown in Table , the methylated surface [Si(111)–CH 3 ] exhibits a high water contact angle (θ water ) of 110.8 ± 0.8°, indicating a very hydrophobic surface.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Steric Spacing of Molecular Linkers on Passivated Si(111) Photoelectrodes

Basile

Pekarek

et al. 2014

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

Surfaces with high photoelectrochemical and electronic quality can be prepared by tethering small molecules to single-crystalline Si(111) surfaces using a two-step halogenation/alkylation method (by Lewis and co-workers).1-7 We report here that the surface coverage of custom-synthesized, phenyl-based molecular linkers can be controlled by varying the steric size of R-groups (R=CH3, C6H11, 2-ethylhexyl) at the periphery of the linker. Additionally, the linkers possess a para triflate group (-O2SCF3) that serves as a convenient analytical marker and as a point of covalent attachment for a redox active label. Quantitative X-ray photoelectron spectroscopy (XPS) measurements revealed that the surface coverage systematically varies according to the steric size of the linker: CH3 (6.7±0.8%), CyHex (2.9±1.2%), EtHex (2.1±0.9%). The stability of the photoelectrochemical cyclic voltammetry (PEC-CV) behavior was dependent on an additional methylation step (with CH3MgCl) to passivate residual Si(111)-Cl bonds. Subsequently, the triflate functional group was utilized to perform Pd-catalyzed Heck coupling of vinylferrocene to the surface-attached linkers. Ferrocene surface coverages measured from cyclic voltammetry on the ferrocene-functionalized surfaces Si(111)-8a/CH3-Fc (R=CH3) and Si(111)-8c/CH3-Fc (R=2-EtHex) are consistent with the corresponding Fe 2p XPS coverages and suggest a ∼1:1 conversion of surface triflate groups to vinyl-Fc sites. The surface defect densities of the linker/CH3 modified surfaces are dependent on the coverage and composition of the organic layer. Surface recombination velocity (SRV) measurements indicated that n-Si(111)-8a/CH3 and the ferrocene coupled n-Si(111)-8a/CH3-Fc exhibited relatively high surface carrier lifetimes (4.51 and 3.88 μs, respectively) and correspondingly low S values (3880 and 4510 cm s(-1)). Thus, the multistep, linker/Fc functionalized surfaces exhibit analogously low trap state densities as compared to the fully passivated n-Si(111)-CH3 surface.

show abstract

Section: Resultsmentioning

confidence: 99%

“… a Average ± standard deviation from three separate samples, two different spots for each sample. b Value from ref . …”

Section: Resultsmentioning

confidence: 99%

Steric Spacing of Molecular Linkers on Passivated Si(111) Photoelectrodes

Basile

Pekarek

et al. 2014

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…Previously, similar nonlinear-optical experiments were modeled by tensorial calculations (11)(12)(13), which are based on the symmetry of the underlying Si lattice. However, our data emphasize that chemistry takes place in real time at the atomic scale and that symmetry is an end result of chemical processes; i.e., it is not constant but evolves in time.…”

Section: Resultsmentioning

confidence: 99%

Measurement and control of in-plane surface chemistry during the oxidation of H-terminated (111) Si

Gökce

Adles

Aspnes

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

In-plane directional control of surface chemistry during interface formation can lead to new opportunities regarding device structures and applications. Control of this type requires techniques that can probe and hence provide feedback on the chemical reactivity of bonds not only in specific directions but also in real time. Here, we demonstrate both control and measurement of the oxidation of H-terminated (111) Si. Control is achieved by externally applying uniaxial strain, and measurement by second-harmonic generation (SHG) together with the anisotropic-bond model of nonlinear optics. In this system anisotropy results because bonds in the strain direction oxidize faster than those perpendicular to it, leading in addition to transient structural changes that can also be detected at the bond level by SHG.silicon | hyperpolarizability | ellipsometry | metrology | optical T he oxidation of silicon is one of the most technologically important chemical reactions. Because dangling bonds trap and/ or scatter carriers, well-organized bonding at Si∕SiO 2 interfaces is critical to device performance. Therefore, although Si oxidation has been studied for many years, the formation dynamics of Si∕SiO 2 interfaces continues to be of interest. The information provided to date regarding oxidation kinetics has been obtained primarily by standard spectroscopic and microscopic structuralanalysis techniques. For example, scanning tunneling microscopy and atomic force microscopy (AFM) studies have revealed the role of surface morphology during oxidation (1, 2). IR absorption experiments have probed the changes in vibrational modes during oxidation and have provided information about the chemical reactions involved in the process (3). Spectroscopic ellipsometry has provided data about growth rates (4). At the same time, considerable effort has been invested in manipulating Si oxidation kinetics. For example, uni-and biaxial strains have been used in manufacturing Si-based devices, taking advantage of the fact that tensile stress increases the overall oxidation rate of thermally grown oxides (5).The effect of strain on the morphology of clean vicinal and on-axis Si surfaces has been well studied by microscopic methods (6, 7). However, an atomic-level understanding of the specific effects of strain on surface chemistry is presently unknown. Here, we investigate oxidation of strained and unstrained H-terminated (111) Si in real time using second-harmonic generation (SHG), and we analyze these data with the anisotropic-bond model (ABM) of nonlinear optics. The bond-specific information that we obtain reveals two important aspects of the relevant chemical dynamics. First, strain changes the oxidation rates of Si─Si back bonds that are oriented in different directions, and second, the average back-bond directions themselves change as a result of this anisotropic oxidation. Fig. 1 provides an atomic-level view of the configuration, showing the bonding of the outermost bilayer of a (111) Si surface. Each outer-layer Si atom has one "up" bon...

show abstract

“…[4,21] We have demonstrated that the interfacial electronic structure of well prepared Si(111)-H, as determined by SHG, can be stable for >10 4 minutes! [4] (Fig. 2) However, intense laser illumination can lead to accelerated, photon-driven reactivity (Fig.…”

Section: Second Harmonic Spectroscopy Of Chemically Modified Semicondmentioning

confidence: 92%

Real Time Dynamics of Laser Activated Interface Processes at the Molecular Scale

Borguet¹

2007

View full text Add to dashboard Cite

Photoreactivity of Si(111)−H in Ambient

Cited by 9 publications

References 50 publications

Steric Spacing of Molecular Linkers on Passivated Si(111) Photoelectrodes

Steric Spacing of Molecular Linkers on Passivated Si(111) Photoelectrodes

Measurement and control of in-plane surface chemistry during the oxidation of H-terminated (111) Si

Real Time Dynamics of Laser Activated Interface Processes at the Molecular Scale

Contact Info

Product

Resources

About