Dynamic parameter estimation of atomic layer deposition kinetics applied to in situ quartz crystal microbalance diagnostics

Holmqvist, Anders; Törndahl, Tobias; Magnusson, Fredrik; Zimmermann, Uwe; Stenström, Stig

doi:10.1016/j.ces.2014.02.005

Cited by 14 publications

(9 citation statements)

References 76 publications

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“…There is scarce experimental data to directly quantitatively compare our calculations. Holmqvist et al 9 have constructed a kinetic model for the DEZ/H 2 O process. In their model, which is fitted to experimental QCM data, they present a barrier of 0.43 eV, which is close to the ligand-exchange barrier for diethyl zinc.…”

Section: Discussionmentioning

confidence: 99%

Atomic Layer Deposition of Zinc Oxide: Study on the Water Pulse Reactions from First-Principles

Weckman

Laasonen

2018

J. Phys. Chem. C

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Atomic layer deposition (ALD) of zinc oxide thin films has been under intense research in the past few years. The most common precursors used in this process are diethyl zinc (DEZ) and water. The surface chemistry related to the growth of a zinc oxide thin film via atomic layer deposition is not entirely clear, and the ideal model of the process has been contradicted by experimental data, e.g., the incomplete elimination of the ethyl ligands from the surface and the non-negative mass change during the water pulse. In this work we investigate the surface reactions of water during the atomic layer deposition of zinc oxide. The adsorption and ligand-exchange reactions of water are studied on ethyl-saturated surface structures to grasp the relevant surface chemistry contributing to the deposition process. The complex ethyl-saturated surface structures are adopted from a previous publication on the DEZ/H2O-process, and different configurations are sampled using ab initio molecular dynamics in order to find a suitable minimum structure. Water molecules are found to adsorb exothermically onto the ethyl-covered surface at all the ethyl concentrations considered. We do not observe an adsorption barrier for water at 0 K; however, the adsorption energy for any additional water molecules decreases rapidly at high ethyl concentrations. Ligand-exchange reactions are studied at various surface ethyl coverages. The water pulse ligand-exchange reactions have overall larger activation energies than surface reactions for diethyl zinc pulse. For some of the configurations considered, the reaction barriers may be inaccessible at the process conditions, suggesting that some ligands may be inert toward ligand-exchange with water. The activation energies for the surface reactions show only a weak dependence on the surface ethyl concentration. The sensitivity of the adsorption of water at high ethyl coverages suggests that at high ligand-coverages the kinetics may be somewhat hindered due to steric effects. Calculations on the ethyl-covered surfaces are compared to a simple model containing a single monoethyl zinc group. The calculated activation energy for this model is in line with calculations done on the complex model, but the adsorption of water is poorly described. The weak adsorption bond onto a single monoethyl zinc is probably due to a cooperative effect between the surface zinc atoms. A cooperative effect between water molecules is also observed; however, the effect on the activation energies is not as significant as has been reported for other ALD processes.

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Section: Discussionmentioning

confidence: 99%

Atomic Layer Deposition of Zinc Oxide: Study on the Water Pulse Reactions from First-Principles

Weckman

Laasonen

2018

J. Phys. Chem. C

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“…The diameter and thickness of the substrate are ~22 and ~2 mm, respectively. During reactant exposures, adsorption/desorption and chemical reactions take place between gaseous reactants and hydroxylated surfaces inside and outside the porous media 18,51 . The ALD kinetics will be discussed in Section 3.4.…”

Section: Model and Simulationmentioning

confidence: 99%

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

et al. 2021

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ZnO deposition in porous γ‐Al2O3 via atomic layer deposition (ALD) is the critical first step for the fabrication of zeolitic imidazolate framework membranes using the ligand‐induced perm‐selectivation process (Science, 361 (2018), 1008–1011). A detailed computational fluid dynamics (CFD) model of the ALD reactor is developed using a finite‐volume‐based code and validated. It accounts for the transport processes within the feeding system and reaction chamber. The simulated precursor spatiotemporal profiles assuming no ALD reaction were used as boundary conditions in modeling diethylzinc reaction/diffusion in porous γ‐Al2O3, the predictions of which agreed with experimental electron microscopy measurements. Further simulations confirmed that the present deposition flux is much less than the upper limit of flux, below which the decoupling of reactor/substrate is an accurate assumption. The modeling approach demonstrated here allows for the design of ALD processes for thin‐film membrane formation including the synthesis of metal–organic framework membranes.

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“…In the process industries, applications include control [88,73,92], optimal experimental design [90,106], and parameter estimation [74] of (bio-)chemical reactors.…”

Section: Optimization and Simulation In Science And Engineeringmentioning

confidence: 99%

CasADi: a software framework for nonlinear optimization and optimal control

Andersson

Gillis

Horn³

et al. 2018

Math. Prog. Comp.

2,425

976

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We present CasADi, an open-source software framework for numerical optimization. CasADi is a general-purpose tool that can be used to model and solve optimization problems with a large degree of flexibility, larger than what is associated with popular algebraic modeling languages such as AMPL, GAMS, JuMP or Pyomo. Of special interest are problems constrained by differential equations, i.e. optimal control problems. CasADi is written in self-contained C++, but is most conveniently used via full-featured interfaces to Python, MATLAB or Octave. Since its inception in late 2009, it has been used successfully for academic teaching as well as in applications from multiple fields, including process control, robotics and aerospace. This article gives an up-to-date and accessible introduction to the CasADi framework, which has undergone numerous design improvements over the last seven years.

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Dynamic parameter estimation of atomic layer deposition kinetics applied to in situ quartz crystal microbalance diagnostics

Cited by 14 publications

References 76 publications

Atomic Layer Deposition of Zinc Oxide: Study on the Water Pulse Reactions from First-Principles

Atomic Layer Deposition of Zinc Oxide: Study on the Water Pulse Reactions from First-Principles

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

CasADi: a software framework for nonlinear optimization and optimal control

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