Ab initio H2 desorption pathways for H/Si(100): the role of SiH2(a)

Wu, Christine J.; Ionova, Irina V.; Carter, Emily A.

doi:10.1016/0039-6028(93)90185-m

Cited by 93 publications

(68 citation statements)

References 46 publications

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“…Comparing to the experimental activation energy of desorption of ∼ 58 kcal/mol (2.5 eV) 3,4,17,18 , these findings were interpreted as being compelling evidence against the pre-paring mechanism. In an attempt to reconcile the experimentally observed energetics and kinetics of desorption from the monohydride phase, various defect-mediated mechanisms [6][7][8]12 were suggested including formation of metastable dihydride species as an intermediate step. All the above studies have in common that their argumentation rests on computational schemes based on CI and the small and simple Si 9 H 12 cluster to model the Si(001)-2×1 surface except the work by Nachtigall et al 8 where DFT has been employed.…”

Section: Introductionmentioning

confidence: 99%

Effect of the cluster size in modeling the H2 desorption and dissociative adsorption on Si(001)

Penev¹,

Kratzer²,

Scheffler³

1999

The Journal of Chemical Physics

164

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Three different clusters, Si9H12, Si15H16, and Si21H20, are used in density-functional theory calculations in conjunction with ab initio pseudopotentials to study how the energetics of H2 dissociative adsorption on and associative desorption from Si(001) depends on the cluster size. The results are compared to five-layer slab calculations using the same pseudopotentials and high quality planewave basis set. Several exchange-correlation functionals are employed. Our analysis suggests that the smaller clusters generally overestimate the activation barriers and reaction energy. The Si21H20 cluster, however, is found to predict reaction energetics, with E des a = 56 ± 3 kcal/mol (2.4 ± 0.1 eV), reasonably close (though still different) to that obtained from the slab calculations. Differences in the calculated activation energies are discussed in relation to the efficiency of clusters to describe the properties of the clean Si(001)-2×1 surface.

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Section: Introductionmentioning

confidence: 99%

Effect of the cluster size in modeling the H2 desorption and dissociative adsorption on Si(001)

Penev¹,

Kratzer²,

Scheffler³

1999

The Journal of Chemical Physics

164

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“…Density functional (DF) calculations carried out on slab models [4][5][6][7] suggest the viability of the so-called "pre-pairing" mechanism, where the two hydrogens desorb from the same dimer unit. In contrast, cluster calculations of various degrees of computational sophistication [8][9][10] rule out such a pre-pairing mechanism because of the activation energy is too high (> 3 eV ), and instead predict desorption paths based on isolated silicon dihydride (Sill2) defects [11][12][13][14]. In an attempt to understand the origin of such a discrepancy, ab-initio and DF calculations for small silicon-based molecules have been compared [15].…”

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confidence: 99%

H2 adsorption/desorption at Si(111)-(7 × 7): a density functional study

Vittadini

Selloni

1997

Surface Science

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The interaction of H 2 with the Si( 111 )-(7 x 7) surface is investigated by means of density functional slab calculations on a (4 x 2) reconstructed model surface. A viable mechanism for fll desorption is identified, which involves thermally activated Sill 2 units at adatom sites. This mechanism leads to adsorption and desorption barriers of 1.0 and 2.4 eV, respectively, in agreement with experiment. An explanation for the two components observed in the ~ peak of temperature-programmed desorption spectra is proposed. The lattice deformation energy at the transition state for desorption is large (~ 0.6 eV ). If we assume that this remains in the surface after H 2 desorption, the low translational energy of desorbing molecules which has been observed experimentally can in part be explained. © 1997 Elsevier Science B.V.

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“…44 In the case of H/Si, theoretical investigations indicate that the diffusion 19,28,32 and desorption barriers 18 decrease substantially when the Si atoms relax. However, a model involving static lattice distortion of silicon between the two ''hydrogen-adsorbed'' and ''hydrogen-desorbed'' states, and a corresponding barrier change, would lead to a violation of detailed balance.…”

Section: Introductionmentioning

confidence: 99%

Reaction dynamics of molecular hydrogen on silicon surfaces

et al. 1996

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Bratu, P.; Brenig, W.; Gross, A.; Hartmann, M.; Höfer, U.; Kratzer, Peter; Russ, R. Published in:Physical Review B Link to article, DOI:10.1103/PhysRevB.54.5978 Publication date: 1996 Document VersionPublisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Bratu, P., Brenig, W., Gross, A., Hartmann, M., Höfer, U., Kratzer, P., & Russ, R. (1996). Reaction dynamics of molecular hydrogen on silicon surfaces. Physical Review B, 54(8), 5978-5991. DOI: 10.1103/PhysRevB.54.5978 Reaction dynamics of molecular hydrogen on silicon surfaces Experimental and theoretical results on the dynamics of dissociative adsorption and recombinative desorption of hydrogen on silicon are presented. Using optical second-harmonic generation, extremely small sticking probabilities in the range 10 Ϫ9 Ϫ10 Ϫ5 could be measured for H 2 and D 2 on Si͑111͒7ϫ7 and Si͑100͒2ϫ1.Strong phonon-assisted sticking was observed for gases at 300 K and surface temperatures between 550 K and 1050 K. The absolute values as well as the temperature variation of the adsorption and desorption rates show surprisingly little isotope effect, and they differ only little between the two surfaces. These results indicate that tunneling, molecular vibrations, and the structural details of the surface play only a minor role for the adsorption dynamics. Instead, they appear to be governed by the localized H-Si bonding and Si-Si lattice vibrations. Theoretically, an effective five-dimensional model is presented taking lattice distortion, corrugation, and molecular vibrations into account within the framework of coupled-channel calculations. While the temperature dependence of the sticking is dominated by lattice distortion, the main effect of corrugation is a reduction of the preexponential factor by about one order of magnitude per lateral degree of freedom. Molecular vibrations have practically no effect on the adsorption/desorption dynamics itself, but lead to vibrational heating in desorption with a strong isotope effect. Ab initio calculations for the H 2 interaction with the dimers of Si͑100͒2 ϫ1 show properties of the potential surface in qualitative agreement with the model, but its dynamics differs quantitatively from the experimental results. ͓S0163-1829͑96͒01732-8͔

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Ab initio H2 desorption pathways for H/Si(100): the role of SiH2(a)

Cited by 93 publications

References 46 publications

Effect of the cluster size in modeling the H2 desorption and dissociative adsorption on Si(001)

Effect of the cluster size in modeling the H2 desorption and dissociative adsorption on Si(001)

H2 adsorption/desorption at Si(111)-(7 × 7): a density functional study

Reaction dynamics of molecular hydrogen on silicon surfaces

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