Electronic structure of the Si(001)2 × 1:H surface and pathway for H2 desorption

Li, Guangwei; Chang, Yia‐Chung; Tsu, R.; Greene, J. E.

doi:10.1016/0039-6028(95)00238-3

Cited by 22 publications

(10 citation statements)

References 21 publications

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“…18 Wu, Ionova, and Carter, on the other hand, searched for a prepairing TS at the Hartree-Fock self-consistent field level ͑HFSCF͒ and were unable to find a TS for direct H 2 desorption from the dimer, presumably because of the lower level of theory they used. 19 Theoretical support for H 2 desorption via the prepairing mechanism comes from several DFT calculations, [20][21][22][23][24] which find an activation barrier within the range of experimental values. These calculations include several six-layer slab calculations using C s symmetry.…”

Section: Kinetics Of H 2 Adsorption/desorptionmentioning

confidence: 96%

“…These calculations include several six-layer slab calculations using C s symmetry. 20,22,24 Li et al 24 used the localdensity approximation ͑LDA͒ with a 6-Ry cutoff, and found a symmetric ͑TS͒ with an activation barrier of 2.67 eV ͑not including zpe corrections͒. Using a 12-Ry cutoff and a combined LDA, generalized gradient approximation approach ͑LDA-GGA͒, in which electronic densities calculated using LDA are used as input for the nonlocal exchange-correlation term in the GGA, Vittadini and Selloni 22 found an asymmetric side-centered TS with an energy barrier for desorption of 2.4 eV ͑not including zpe corrections͒.…”

Section: Kinetics Of H 2 Adsorption/desorptionmentioning

confidence: 99%

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A dynamically and kinetically consistent mechanism forH2adsorption/desorption from Si(100)-2×1

Radeke

Carter

1996

Phys. Rev. B

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Curiously, H 2 desorption from Si͑100͒-2ϫ1 follows approximately first-order kinetics rather than the expected second-order kinetics, arousing interest about the mechanism involved in the desorption process. We investigate the energetics and rate constants of three proposed mechanisms for H 2 desorption from Si͑100͒-2ϫ1, namely, the prepairing mechanism, the isomerization mechanism, and the isolated dihydride mechanism, using complete active space self-consistent-field and multireference single-and double-excitation configuration-interaction calculations. We find the desorption barrier for the isolated dihydride mechanism to be 2.49 eV, the only barrier in excellent agreement with the experimentally determined barrier ͑ϳ2.5 eV͒. The isolated dihydride mechanism also provides the only calculated desorption rate constant close to experimental values. Finally, we show that this mechanism is able to explain the experimentally observed apparent violation of detailed balance of H 2 adsorption/desorption on Si͑100͒, as well as other experimentally observed dynamics. ͓S0163-1829͑96͒07939-8͔

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Section: Kinetics Of H 2 Adsorption/desorptionmentioning

confidence: 96%

Section: Kinetics Of H 2 Adsorption/desorptionmentioning

confidence: 99%

A dynamically and kinetically consistent mechanism forH2adsorption/desorption from Si(100)-2×1

Radeke

Carter

1996

Phys. Rev. B

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“…In the model already introduced above, two hydrogen atoms from doubly occupied dimers recombine and desorb through a symmetric 37 or more likely an asymmetric transition state. 30,33,35,36 These models are in agreement with the desorption kinetics, and slab calculations based on density functional theory give the experimental activation energy for the desorption.…”

Section: Discussion Of Microscopic Mechanismsmentioning

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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“…More experimental results were reported in Ref. 8,24 However, it is interesting to note the quasi-independence of Si 0.7 Ge 0.3 growth rate on temperature. At lower misfit, strain is relaxed by the injection of misfit dislocations when the layer thickness surpasses the critical thickness calculated using a kinetical model.…”

Section: Resultsmentioning

confidence: 71%

“…The critical thickness at which Si 1Ϫx Ge x layers become wavy decreases to 5 and 2.5 nm at germanium fractions of 0.4 and 0.5, respectively. 24 Hydrogen desorption is known to be the limiting step of Si growth in low temperature chemical vapor deposition ͑CVD͒. 18.…”

Section: Resultsmentioning

confidence: 99%

Epitaxy of Si/Si1−xGex heterostructures with very small roughness using a production-compatible ultrahigh vacuum-chemical vapor deposition reactor

Lafontaine

1998

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Growth and characterization of ultrahigh vacuum/chemical vapor deposition SiGe epitaxial layers on bulk singlecrystal SiGe and Si substratesTwo different roughening mechanisms are studied using a production-ready epitaxial deposition system to grow various epilayers, including the base layer of bipolar transistors. Surface roughness is measured using atomic force microscopy and transmission electron microscopy is used for cross-sectional analysis. Very smooth surfaces are routinely obtained, with a root mean square roughness of 0.15 nm. However, two possible mechanisms are shown to increase surface roughness under certain conditions. Above a certain critical thickness, for growth temperatures higher than 525°C and Ge compositions above 25%, strain redistribution results in surface ripples with a typical wavelength of the order of 100 nm. In addition, we find that substrate contamination ͑C,O͒ can produce wide depressions, several hundreds of nm wide and on average 10 nm deep in Si epilayers. The addition of a small concentration of Ge ͑below 15%͒ seems to produce more planar growth compared to the same thickness ͑50 nm͒ of Si only. The origin of the different surface morphologies observed is discussed.

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Electronic structure of the Si(001)2 × 1:H surface and pathway for H2 desorption

Cited by 22 publications

References 21 publications

A dynamically and kinetically consistent mechanism forH2adsorption/desorption from Si(100)-2×1

A dynamically and kinetically consistent mechanism forH2adsorption/desorption from Si(100)-2×1

Reaction dynamics of molecular hydrogen on silicon surfaces

Epitaxy of Si/Si1−xGex heterostructures with very small roughness using a production-compatible ultrahigh vacuum-chemical vapor deposition reactor

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