The Si (100) surface. III. Surface reconstruction

Appelbaum, Joel A.; Baraff, G. A.; Hamann, D. R.

doi:10.1103/physrevb.14.588

Cited by 209 publications

(87 citation statements)

References 16 publications

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“…In order to understand the difference in appearance of "clean" and "monohydride" dimers, it is important to understand the basic symmetry In the bulk-truncated Si(001) surface, each surface Si atom has two sigma bonds to the bulk substrate (labeled "as") and two half-filled, sp 3 -hybridized dangling bonds (labeled "sp 3 "). As originally noted by Appelbaum and co-workers 32 , the formation of a dimer can be understood as a rehybridization of these four sp 3 -hybridized "dangling bonds" into molecular orbitals of the dimer which can be described as a, x, o*, and n* in nature. The a bond is quite strong but the x bond is weak, with the result that the energy difference between the occupied x state and the unoccupied x* state is small, less than 1 eV.…”

Section: Methodsmentioning

confidence: 99%

Direct dimer-by-dimer identification of clean and monohydride dimers on the Si(001) surface by scanning tunneling microscopy

Wang¹,

Bronikowski²,

Hamers³

1994

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Atomic resolution images of clean Si(001)-(2×1) and the monohydride phase, Si(001)-(2×1)H were investigated using scanning tunneling microscopy at various sample-tip bias voltages. At a sample-tip bias of −1.9 V, each dimer of the monohydride phase shows two protrusions 3.3 Å apart separated by a minimum 0.12 Å deep, while clean dimers show a single protrusion per unit cell. Monohydride dimers appear lower than ‘‘clean’’ dimers, with apparent height differences ranging from 1.9 Å at −1.6 V to 0.65 Å at −3.0 V sample bias. An analysis of the apparent height and spatial distribution of tunneling current within each dimer can be used to unambiguously discriminate between clean dimers, monohydride dimers, and vacancy defects. This methodology is applied to study the distribution of hydrogen on Si(001) surfaces during chemical vapor deposition using disilane, revealing segregation of the monohydride into nearly isotropic islands.

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Section: Methodsmentioning

confidence: 99%

Direct dimer-by-dimer identification of clean and monohydride dimers on the Si(001) surface by scanning tunneling microscopy

Wang¹,

Bronikowski²,

Hamers³

1994

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…[12][13][14] This makes the surface very reactive. Redondo and Goddard 15 first demonstrated that a silicon surface with singlet diradical dimers can be correctly described only with a multireference wave function.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Water on the Si(100) Surface: An Ab Initio and QM/MM Cluster Study

2001

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The adsorption of water on the Si(100) surface is investigated using ab initio quantum chemical cluster calculations. A reaction profile is constructed using the multiconfigurational SCF method. The calculations demonstrate that the reactant should be described with a multireference wave function in order to obtain correct energetics, because it contains a bare dimer with significant diradical character. The system becomes almost single-configurational as water approaches the surface and forms a molecularly adsorbed intermediate. Therefore, except for the reactant, a single-configurational wave function seems to be sufficient for a correct description of the reaction. The adsorbed OH group in an isolated product can nearly freely rotate between the trans and gauche minima. Interactions between the OH groups and the dangling bonds are small and do not appear to change the OH orientation. However, the interdimer hydrogen bonding is stronger and forces the OH orientation to be perpendicular to the dimer bond. The free rotation of the OH group in an isolated dimer model and the hydrogen-bonding picture in an extended cluster model are consistent with the experimental finding for the OH orientation in the product. Si9H12, Si15H16, Si32H28, Si48H36, and Si64H44cluster models for the Si(100) surface are used, and the SIMOMM (surface integrated molecular orbital molecular mechanics) method is used effectively for these large cluster calculations. The SIMOMM and full quantum results are compared. Disciplines Chemistry CommentsReprinted ( The adsorption of water on the Si(100) surface is investigated using ab initio quantum chemical cluster calculations. A reaction profile is constructed using the multiconfigurational SCF method. The calculations demonstrate that the reactant should be described with a multireference wave function in order to obtain correct energetics, because it contains a bare dimer with significant diradical character. The system becomes almost single-configurational as water approaches the surface and forms a molecularly adsorbed intermediate. Therefore, except for the reactant, a single-configurational wave function seems to be sufficient for a correct description of the reaction. The adsorbed OH group in an isolated product can nearly freely rotate between the trans and gauche minima. Interactions between the OH groups and the dangling bonds are small and do not appear to change the OH orientation. However, the interdimer hydrogen bonding is stronger and forces the OH orientation to be perpendicular to the dimer bond. The free rotation of the OH group in an isolated dimer model and the hydrogen-bonding picture in an extended cluster model are consistent with the experimental finding for the OH orientation in the product. Si 9 H 12 , Si 15 H 16 , Si 32 H 28 , Si 48 H 36 , and Si 64 H 44 cluster models for the Si(100) surface are used, and the SIMOMM (surface integrated molecular orbital molecular mechanics) method is used effectively for these large cluster calculations. The SIMOMM and full q...

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“…22 The resulting k r values are given in the inset. We observe, expectedly, k Memb to drop significantly with decreasing d due to dispersion modification as well as the reduction of phonon mean free paths (MFP) caused by diffuse boundary scattering at the surfaces as a result of their reconstruction at the equilibrium state [23]. These effects been studied experimentally in the literature in the context of a thin silicon layer on a substrate [24], freestanding silicon membranes [12,25], and also silicon nanowires [26].…”

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confidence: 99%

Thermal transport size effects in silicon membranes featuring nanopillars as local resonators

Honarvar

Yang

Hussein

2016

Applied Physics Letters

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Silicon membranes patterned by nanometer-scale pillars standing on the surface provide a practical platform for thermal conductivity reduction by resonance hybridization. Using molecular simulations, we investigate the effect of nanopillar size, unit-cell size, and finite-structure size on the net capacity of the local resonators in reducing the thermal conductivity of the base membrane. The results indicate that the thermal conductivity reduction increases as the ratio of the volumetric size of a unit nanopillar to that of the base membrane is increased, and the intensity of this reduction varies with unit-cell size at a rate dependent on the volumetric ratio. Considering sample size, the resonance-induced thermal conductivity drop is shown to increase slightly with the number of unit cells until it would eventually level off.In semiconducting materials, heat is carried mostly by phonons which are quanta of lattice vibrations [1]. This provides an opportunity to introduce significant changes to the thermal transport properties by direct engineering of the phonon characteristics−which are shaped primarily by the phonon band structure and the nature of the underlying scattering mechanisms [2]. Recent reviews survey developments in theory, computation, and experiment pertaining to nanoscale thermal transport in a variety of materials and point to the remarkable possibilities for using nanostructuring as a means for phonon engineering [3].Thermoelectric energy conversion stands to benefit profoundly from the ability to alter the phonon properties by nanostructuring [4], as well as by reducing the material dimensionality [5]. Thermoelectric materials, which generate electricity from heat and vice versa, are characterized by a figure of merit defined as ZT = σT S 2 /k, where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity (consisting of a lattice component and an electrical component), and T is absolute temperature [6]. One strategy to improve the value of ZT , particularly in semiconductors, is to reduce the lattice thermal conductivity and attempt to do so without negatively affecting S and σ. A promising approach for achieving this goal is to introduce nanoscale local resonators as intrinsic substructures within, or attached to, a host crystalline material [7,8]. The emerging system, called nanophononic metamaterial (NPM), exhibits unique properties that are not attainable in conventional nanostructured media such as nanocomposites [9] or nanophononic crystals [10]. The substructure resonances, which could be numerous for relatively large substructures, may be tuned to couple with all or most of the heat-carrying phonon modes of the underlying host medium. This atomic-scale coupling mechanism is essentially a resonance hybridization between the wavenumberdependent wave modes of the host medium (phonons) and the wavenumber-independent vibration modes of the local substructure (vibrons). The outcome is significant reductions in the phonon group velocities across roughly ...

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The Si (100) surface. III. Surface reconstruction

Cited by 209 publications

References 16 publications

Direct dimer-by-dimer identification of clean and monohydride dimers on the Si(001) surface by scanning tunneling microscopy

Direct dimer-by-dimer identification of clean and monohydride dimers on the Si(001) surface by scanning tunneling microscopy

Adsorption of Water on the Si(100) Surface: An Ab Initio and QM/MM Cluster Study

Thermal transport size effects in silicon membranes featuring nanopillars as local resonators

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