Mechanism and Kinetics of Nonequilibrium and Multilayer Adsorption and Desorption of Gases on Solids

Juneja, Harpreet; Iqbal, Asad; Yao, Junpin; Shadman, Farhang

doi:10.1021/ie060475k

Cited by 5 publications

(10 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We now consider how realistic these models are in the context that under realistic ALD conditions such a “dry ambient” is far from what actually occurs. In fact, it is well-known that water molecules may be adsorbed from the gas phase forming multilayers on the surfaces of various oxides, such as Al 2 O 3 , TiO 2 , SiO 2 , SnO 2 , ZrO 2 , – and HfO 2 . , It is found that the first adsorbed layer is strongly bonded to the surface by chemisorption and that the second layer is strongly bonded to the first chemisorbed layer by physisorption. Additional layers are all physisorbed with slowly diminishing bonding strength that approaches the bonding strength of liquid water.…”

Section: Resultsmentioning

confidence: 99%

“…Additional layers are all physisorbed with slowly diminishing bonding strength that approaches the bonding strength of liquid water. ZrO 2 and HfO 2 show especially high adsorption loading due to their higher polarity and higher site density . Hence, under high water partial pressures, such as occurs during the water pulse of HfO 2 ALD, it is quite likely that several layers of water molecules will be accommodated on the HfO 2 surface.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Atomic Layer Deposition of Hafnium Oxide from Hafnium Chloride and Water

2008

View full text Add to dashboard Cite

Hafnium oxide (HfO2) is a leading candidate to replace silicon oxide as the gate dielectric for future generation metal-oxide-semiconductor based nanoelectronic devices. Atomic layer deposition (ALD) has recently gained interest because of its suitability for fabrication of conformal films with thicknesses in the nanometer range. This study uses periodic density functional theory (DFT) to investigate the mechanisms of both half-reactions occurring on the growing surface during the ALD of HfO2 using HfCl4 and water as precursors. We find that the adsorption energy and the preferred site of adsorption of the metal precursor are strong functions of the water coverage. As water coverage increases, the metal precursor preferentially interacts with multiple surface adsorption sites. During the water pulse the removal of Cl can be facilitated by either a ligand exchange reaction or the dissociation of Cl upon increase in coordination of the Hf atom of the precursor. Our predicted potential energy surface indicates that a more likely mechanism is hydration of the adsorbed Hf complex up to a coordination number of 7, followed by the dissociation of a chloride ion that is stabilized by solvation. Born-Oppenheimer molecular dynamics (BOMD) simulations of an adsorbed metal precursor in the presence of a multilayer of water shows that Cl dissociation is facile if sufficient water molecules are present to solvate the Cl(-) anions. Hence, solvation plays a crucial role during the water pulse and provides an alternative explanation for why ALD growth rates for this system decrease at high temperatures.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Atomic Layer Deposition of Hafnium Oxide from Hafnium Chloride and Water

2008

View full text Add to dashboard Cite

show abstract

“…The major advantage of this model compared with the adsorption models reported previously [ 5 , 26 – 30 ] is that it includes spatial heterogeneity and also considers growth of the surface due to absorbed material in the explicit form. Although this feature is critical for thrombus growth, this model can also be of importance for many other fields, such as physics, chemistry, and biology.…”

Section: Discussionmentioning

confidence: 99%

Continuous Modeling of Arterial Platelet Thrombus Formation Using a Spatial Adsorption Equation

et al. 2015

View full text Add to dashboard Cite

In this study, we considered a continuous model of platelet thrombus growth in an arteriole. A special model describing the adhesion of platelets in terms of their concentration was derived. The applications of the derived model are not restricted to only describing arterial platelet thrombus formation; the model can also be applied to other similar adhesion processes. The model reproduces an auto-wave solution in the one-dimensional case; in the two-dimensional case, in which the surrounding flow is taken into account, the typical torch-like thrombus is reproduced. The thrombus shape and the growth velocity are determined by the model parameters. We demonstrate that the model captures the main properties of the thrombus growth behavior and provides us a better understanding of which mechanisms are important in the mechanical nature of the arterial thrombus growth.

show abstract

“…There are a number of theoretical adsorption reaction models [11][12][13][14][15][16][17][18], based on the Langmuir [19,20] or BET [21] isotherms, (in the case study of the BET kinetic model, a simple analytical solution has only recently been found [22]), as well as theoretical adsorption diffusion models, based on second law. The adsorption diffusion models [23][24][25][26][27][28][29] are differentiated by the possible combinations of the three diffusion steps that govern the overall process: (i) liquid film diffusion, (ii) pore diffusion and (iii) surface diffusion.…”

Section: Introductionmentioning

confidence: 99%

Load-dependent surface diffusion model for analyzing the kinetics of protein adsorption onto mesoporous materials

Marbán

Ramírez-Montoya

García

et al. 2018

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

The adsorption of cytochrome c in water onto organic and carbon xerogels with narrow pore size distributions has been studied by carrying out transient and equilibrium batch adsorption experiments. It was found that equilibrium adsorption exhibits a quasi-Langmuirian behavior (a g coefficient in the Redlich-Peterson isotherms of over 0.95) involving the formation of a monolayer of cyt c with a depth of ∼4nm on the surface of all xerogels for a packing density of the protein inside the pores of 0.29gcm. A load-dependent surface diffusion model (LDSDM) has been developed and numerically solved to fit the experimental kinetic adsorption curves. The results of the LDSDM show better fittings than the standard homogeneous surface diffusion model. The value of the external mass transfer coefficient obtained by numerical optimization confirms that the process is controlled by the intraparticle surface diffusion of cyt c. The surface diffusion coefficients decrease with increasing protein load down to zero for the maximum possible load. The decrease is steeper in the case of the xerogels with the smallest average pore diameter (∼15nm), the limit at which the zero-load diffusion coefficient of cyt c also begins to be negatively affected by interactions with the opposite wall of the pore.

show abstract

Mechanism and Kinetics of Nonequilibrium and Multilayer Adsorption and Desorption of Gases on Solids

Cited by 5 publications

References 26 publications

Atomic Layer Deposition of Hafnium Oxide from Hafnium Chloride and Water

Atomic Layer Deposition of Hafnium Oxide from Hafnium Chloride and Water

Continuous Modeling of Arterial Platelet Thrombus Formation Using a Spatial Adsorption Equation

Load-dependent surface diffusion model for analyzing the kinetics of protein adsorption onto mesoporous materials

Contact Info

Product

Resources

About