Adsorption kinetics of CO on Cr/Ru surfaces

Denecke, R.; Tränkenschuh, B.; Engelhardt, Marina; Steinrück, Hans‐Peter

doi:10.1016/s0039-6028(03)00170-5

Cited by 9 publications

(5 citation statements)

References 15 publications

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“…the type of precursors. Comparing with experimental results from [17,21], we can roughly say that the sticking of incident molecules with a low level of energy corresponds to the domain with k < 1.…”

Section: Sticking Coefficientsupporting

confidence: 52%

“…The transition from Langmuir to precursor type generally depends on the energy of the incoming particles and the substrate surface conditions. Experimental results in [17,21] show that a higher energy of incident molecules leads to an overall lower sticking coefficient, a change in the sticking mechanism from precursor to Langmuir type. Following the theoretical study by Kisliuk [22,23], a general function of a coverage dependent sticking coefficient can be obtained as…”

Section: Sticking Coefficientmentioning

confidence: 98%

“…Generally, α i is a function of temperature, the surface roughness and the surface coverage (θ i , the compound fraction) [15][16][17][18][19][20][21]. In the well-known Langmuir kinetics, the chemical adsorption at the surface is proportional to the extent of available impact sites on the surface.…”

Section: Sticking Coefficientmentioning

confidence: 99%

“…A common expression for α i in the Langmuir kinetics is α i0 (1 − θ i ), where α i0 is called the initial sticking coefficient 1 . However, experimental results show that this linear relation often underestimates the sticking coefficient [16,17,20,21]. Physically, this is because the incident molecules can be accommodated not only on the empty sites by chemisorption but also the occupied sites by physisorption and, later, diffusion to the empty sites for chemisorption [15,22,23].…”

Section: Sticking Coefficientmentioning

confidence: 99%

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Effects of variable sticking coefficients on the stability of reactive sputtering process

Li¹,

Hsieh²

2004

J. Phys. D: Appl. Phys.

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In reactive sputtering, the introduction of a reactive gas can lead to a hysteresis transition from metal to compounds in both the target and substrate. The hysteresis transition is characterized by a sudden change in partial pressure, sputtering rate, fraction of compound formation, etc. Therefore, stability is an important issue in the process control. In this paper, a mathematical model with variable sticking coefficients based on surface kinetics is used to study the stability of the process. The variable sticking coefficient represents different mechanisms for surface reactions from the Langmuir to precursor type. In order to facilitate the analysis, several nondimensional parameters are identified and used for formulation. Results show that an unsteady system converges to a steady state relatively fast at low inflow rates. With an eigenvalue analysis, the range of positive eigenvalues is consistent with the presence of a hysteresis loop. It is also found that when the chemical reaction on the substrate is moderate, a higher sputter yield of the compound leads to a more stable steady state at lower inflow rates. Regarding the sticking mechanism, for the type of precursors with the parameter k < 1, the compound is easier to form and saturate on the surface due to the higher default sticking coefficient and the lower operating conditions for the hysteresis transition.

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Section: Sticking Coefficientsupporting

confidence: 52%

Section: Sticking Coefficientmentioning

confidence: 98%

Section: Sticking Coefficientmentioning

confidence: 99%

Section: Sticking Coefficientmentioning

confidence: 99%

See 2 more Smart Citations

Effects of variable sticking coefficients on the stability of reactive sputtering process

Li¹,

Hsieh²

2004

J. Phys. D: Appl. Phys.

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“…The site density is chosen as 1 monolayer (i.e., 1.58 × 10 19 sites/m 2 ) on Ru (0001), which corresponds to 2.623 × 10 –09 mol/cm 2 . The probable values of sticking coefficients for the adsorbing species (CO 2 , CO, H 2 O, CH 4 , H 2 ) are chosen as reported in the literature. − Values of binding energies for most of the species are taken from DFT literature. DFT is one of the most accurate approximations at the microscale that is also practical to use nowadays.…”

Section: Methodsmentioning

confidence: 99%

Microkinetic Modeling and Analysis of CO₂ Methanation on Ruthenium

Raghu

Kaisare

2020

Ind. Eng. Chem. Res.

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The catalytic reduction of CO 2 to methane, called CO 2 methanation or the Sabatier reaction, is a reversible and exothermic reaction. A mean field microkinetic model is developed for the Sabatier reaction on Ru catalyst at atmospheric pressure and validated with reactor simulations in this work. The mechanism comprised of elementary steps occurring on the catalyst surface is devised based on spectroscopic findings and DFT calculations reported in the literature. The initial parameter values are taken from DFT literature or computed using UBI-QEP. The model is fitted to limited experimental data points from only one source in the literature. The resulting model reliably predicts experimental data from multiple sources in the literature for CO 2 methanation on Ru at various feed ratios in the temperature range of 250−490 °C as well as the equilibrium conversion of CO 2 . Microkinetic analyses under the relevant conditions revealed that the reaction proceeds via the CO 2 * → CO* → C* → CH x * pathway on Ru catalyst.

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