Quantum Mechanical Investigation of the Influence of the Local Environment on the Vibrational Properties of Hydrogenated Si(111)

Juárez, Fernanda; Patrito, E.M.; Paredes-Olivera, Patricia A.

doi:10.1021/jp808104f

Cited by 11 publications

(16 citation statements)

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“…The partial coverage can be detected by IR spectroscopy 41 because the local environment affects the SiH and SiCl stretching frequencies, as we showed in previous work. 42 Taking into account that SiH and SiCl surface groups have such different reactivities, the partial chlorination of the surface may be viewed as a tool to functionalize the surface selectively at the highly reactive SiCl surface sites.…”

Section: Reactionmentioning

confidence: 99%

On the Mechanism of Silicon Activation by Halogen Atoms

2011

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Despite the widespread use of chlorinated silicon as the starting point for further functionalization reactions, the high reactivity of this surface toward a simple polar molecule such as ammonia still remains unclear. We therefore undertook a comprehensive investigation of the factors that govern the reactivity of halogenated silicon surfaces. The reaction of NH3 was investigated comparatively on the Cl-Si(100)-2 × 1, Br-Si(100)-2 × 1, H-Si(100)-2 × 1, and Si(100)-2 × 1 surfaces using density functional theory. The halogenated surfaces show considerable activation with respect to the hydrogenated surface. The reaction on the halogenated surfaces proceeds via the formation of a stable datively bonded complex in which a silicon atom is pentacoordinated. The activation of the halogenated Si(100)-2 × 1 surfaces toward ammonia arises from the large redistribution of charge in the transition state that precedes the breakage of the Si-X bond and the formation of the Si-NH2 bond. This transition state has an ionic nature of the form Si-NH3(+)X(-). Steric effects also play an important role in surface reactivity, making brominated surfaces less reactive than chlorinated surfaces. The overall activation-energy barriers on the Cl-Si(100)-2 × 1 and Br-Si(100)-2 × 1 surfaces are 12.3 and 19.9 kcal/mol, respectively, whereas on the hydrogenated Si(100)-2 × 1 surface the energy barrier is 38.3 kcal/mol. The reaction of ammonia on the chlorinated surface is even more activated than on the bare Si(100)-2 × 1 surface, for which the activation barrier is 21.3 kcal/mol. Coadsorption effects in partially aminated surfaces and in the presence of reaction products increase activation-energy barriers and have a blocking effect for further reactions of NH3.

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Section: Reactionmentioning

confidence: 99%

On the Mechanism of Silicon Activation by Halogen Atoms

2011

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“…After an exposure time of 3 min at a temperature of 95 °C, a 50% chlorine coverage is obtained . The chlorination can be monitored by the IR frequency shifts of the Si–H and Si–Cl stretching modes, as they are sensitive to the local environment. , …”

Section: Introductionmentioning

confidence: 99%

Tailoring the Surface Reactivity of Silicon Surfaces by Partial Halogenation

2013

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Density functional theory was used to investigate the reactivity of partially chlorinated and stepped silicon surfaces with molecules having N, O, and S head groups in relation to the development of selectively functionalized surfaces. The activation energy barriers for the formation of Si–N, Si–O, and Si–S bonds by breakage of the Si–Cl bond are very sensitive to steric factors and this fact can be used to tune the surface reactivity. Whereas the fully chlorinated Si(111) surface has high energy barriers in the range 34–64 kcal/mol for the reactions with NH3, H2O, H2S, CH3NH2, CH3OH, and CH3SH molecules, the partially chlorinated surface has much lower barriers in the range 13–34 kcal/mol, indicating that some molecules may react at almost room temperature with the SiCl groups. The reactions of these molecules on SiH groups have high energy barriers for all surfaces (in the range 33–42 kcal/mol) indicating that they form a matrix of unreactive groups around the reactive SiCl sites. Unlike the fully chlorinated Si(111) surface, the SiCl groups on the reconstructed step edges are very reactive, showing the lowest activation energy barriers. The different reactivities of SiCl groups on the terraces and step edges of fully chlorinated stepped silicon surfaces may allow the formation of molecular lines along the reactive step edges.

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“…Hence, there is a need to conduct a study on the strain effect on oxidation kinetics. So far, basic aspects of the initial stages of oxidation of unstrained hydrogen-terminated Si(111) (H–Si(111)) surfaces have been elucidated. ,,, Estimation of the rate of the surface oxidation process, which is especially sensitive to oxygen incorporations, was done by using the Si–H stretching mode as a probe. , Chabal et al found that a non-integer order of 1.5 in the Si–H consumption rate is an indicator of a multistep mechanism of oxidation . In another study by Federico et al, they concluded that perfect hydrogenated Si(111) is unreactive toward H 2 O vapor and O 2 at room temperature according to density functional theory (DFT) .…”

Section: Introductionmentioning

confidence: 99%

“…So far, basic aspects of the initial stages of oxidation of unstrained hydrogen-terminated Si(111) (H−Si(111)) surfaces have been elucidated. 6,15,17,18 Estimation of the rate of the surface oxidation process, which is especially sensitive to oxygen incorporations, was done by using the Si−H stretching mode as a probe. 17,18 Chabal et al found that a non-integer order of 1.5 in the Si−H consumption rate is an indicator of a multistep mechanism of oxidation.…”

Section: Introductionmentioning

confidence: 99%

“…6,15,17,18 Estimation of the rate of the surface oxidation process, which is especially sensitive to oxygen incorporations, was done by using the Si−H stretching mode as a probe. 17,18 Chabal et al found that a non-integer order of 1.5 in the Si−H consumption rate is an indicator of a multistep mechanism of oxidation. 17 In another study by Federico et al, they concluded that perfect hydrogenated Si(111) is unreactive toward H 2 O vapor and O 2 at room temperature according to density functional theory (DFT).…”

Section: Introductionmentioning

confidence: 99%

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Strain Activation of Surface Chemistry on H-Terminated Si(111)

2021

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Manipulation of the chemical and electronic properties of materials by strain is a widely accepted phenomenon. However, the impact of strain on microscopic aspects such as chemical reactivity is not clearly understood at the bond level. Here, we investigated the effect of strain on surface reactivity of H–Si(111). Analysis of FTIR data revealed that a decrease in stretching Si–H band’s intensity and fluctuations in intensity of the bending Si–H mode, which are in relation to the appearance of a new peak, are correlated with each other. The underlying reason for the new peak is the formation of a three-center bond as a result of diffusion of a hydrogen atom from the Si–H site. Our findings show that both the back bonds and the up bonds are easily oxidized due to the strain effect. In particular, the significant point is direct formation of Si–OH without any energy barrier. As strain is applied to the samples, the findings indicate that different oxidation pathways predominate.

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Quantum Mechanical Investigation of the Influence of the Local Environment on the Vibrational Properties of Hydrogenated Si(111)

Cited by 11 publications

References 50 publications

On the Mechanism of Silicon Activation by Halogen Atoms

On the Mechanism of Silicon Activation by Halogen Atoms

Tailoring the Surface Reactivity of Silicon Surfaces by Partial Halogenation

Strain Activation of Surface Chemistry on H-Terminated Si(111)

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