Adsorption and Reaction Mechanisms of Direct Palladium Synthesis by ALD Using Pd(hfac)2 and Ozone on Si (100) Surface

Palladium nanoparticles made by atomic layer deposition (ALD) normally involve formaldehyde or H2 as a reducing agent. Since formaldehyde is toxic and H2 is explosive, it is advantageous to remove this reducing step during the fabrication of palladium metal by ALD. In this work we have successfully used Pd(hfac)2 and ozone directly to prepare palladium nanoparticles, without the use of reducing or annealing agents. Density functional theory (DFT) was employed to explore the reaction mechanisms of palladium metal formation in this process. DFT results show that Pd(hfac)2 dissociatively chemisorbed to form Pd(hfac)* and hfac* on the Si (100) surface. Subsequently, an O atom of the ozone could cleave the C–C bond of Pd(hfac)* to form Pd* with a low activation barrier of 0.46 eV. An O atom of the ozone could also be inserted into the hfac* to form Pd(hfac-O)* with a lower activation barrier of 0.29 eV. With more ozone, the C–C bond of Pd(hfac-O)* could be broken to produce Pd* with an activation barrier of 0.42 eV. The ozone could also chemisorb on the Pd atom of Pd(hfac-O)* to form O3-Pd(hfac-O)*, which could separate into O-Pd(hfac-O)* with a high activation barrier of 0.83 eV. Besides, the activation barrier was 0.64 eV for Pd* that was directly oxidized to PdOx by ozone. Based on activation barriers from DFT calculations, it was possible to prepare palladium without reducing steps when ALD conditions were carefully controlled, especially the ozone parameters, as shown by our experimental results. The mechanisms of this approach could be used to prepare other noble metals by ALD without reducing/annealing agents.

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Mechanisms for the formation of epoxide and chlorine-containing products in the oxidation of ethylene by chromyl chloride: a density functional study

Canadian Journal of Chemistry ◽

10.1139/v99-148 ◽

1999 ◽

Vol 77 (9) ◽

pp. 1476-1491 ◽

Cited By ~ 14

Author(s):

Maricel Torrent ◽

Liqun Deng ◽

Miquel Duran ◽

Miquel Solà ◽

Tom Ziegler

Keyword(s):

Density Functional Theory ◽

Reaction Mechanisms ◽

Density Functional ◽

Activation Barrier ◽

Activation Energies ◽

Functional Study ◽

Functional Theory ◽

Activation Barriers ◽

Density Functional Study ◽

Chromyl Chloride

The reaction between CrO2Cl2 and ethylene leading to the formation of epoxide and chlorohydrin precursors or directly to 1,2-dichloroethane has been studied by density functional theory. The formation of the epoxide precursor (Cl2(O)Cr-OC2H4) was found to take place via a [3+2] addition of ethylene to two Cr=O bonds followed by rearrangement of the five-membered diol to the epoxide product. The alternative mechanisms involving a direct addition of oxygen to ethylene or the [2+2] addition of the olefin to a Cr=O bond were found to have much higher activation energies. The formation of the chlorohydrin precursor (Cl(O)Cr-OCH2=CHCl) was found to take place via a [3+2] addition to one CrCl and one Cr=O bond. Pathways involving initial [2+2] addition to a CrCl or Cr=O bond had much higher activation barriers. The generation of 1,2-dichloroethane is highly unfavorable with an endothermicity of 44.7 kcal/mol and an even higher activation barrier. It is suggested that the formation of epoxide and chlorohydrin from the respective precursors requires the addition of H2O.Key words: reaction mechanisms, epoxide, oxidation of ethylene, chromyl chloride, DFT.

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Balancing the Activity and Selectivity of Propane Oxidative Dehydrogenation on NiOOH (001) and (010)

Transactions of Tianjin University ◽

10.1007/s12209-020-00267-3 ◽

2020 ◽

Vol 26 (5) ◽

pp. 341-351

Author(s):

Lisheng Li ◽

Hua Wang ◽

Jinyu Han ◽

Xinli Zhu ◽

Qingfeng Ge

Keyword(s):

Oxidative Dehydrogenation ◽

Density Functional ◽

Activation Barrier ◽

Propane Oxidative Dehydrogenation ◽

Functional Theory ◽

Activation Barriers ◽

Propylene Oxidation ◽

Propane Odh ◽

High Activation Barrier ◽

Allylic Radical

Abstract Propane oxidative dehydrogenation (ODH) is an energy-efficient approach to produce propylene. However, ODH suffers from low propylene selectivity due to a relatively higher activation barrier for propylene formation compared with that for further oxidation. In this work, calculations based on density functional theory were performed to map out the reaction pathways of propane ODH on the surfaces (001) and (010) of nickel oxide hydroxide (NiOOH). Results show that propane is physisorbed on both surfaces and produces propylene through a two-step radical dehydrogenation process. The relatively low activation barriers of propane dehydrogenation on the NiOOH surfaces make the NiOOH-based catalysts promising for propane ODH. By contrast, the weak interaction between the allylic radical and the surface leads to a high activation barrier for further propylene oxidation. These results suggest that the catalysts based on NiOOH can be active and selective for the ODH of propane toward propylene.

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Initial Growth Mechanism of Atomic Layer Deposited Hafnium Dioxide Using Cyclopentadienyl-Type Precursor: A Density Functional Theory Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1120-1121.16 ◽

2015 ◽

Vol 1120-1121 ◽

pp. 16-20

Author(s):

Guang Fen Zhou ◽

Jie Ren

Keyword(s):

Density Functional ◽

Activation Barrier ◽

Atomic Layer ◽

Hafnium Dioxide ◽

Initial Growth ◽

Elimination Reaction ◽

Growth Mechanisms ◽

Functional Theory ◽

Barrier Analysis ◽

Layer Deposition

The initial growth mechanisms of atomic layer deposition of Hafnium dioxide thin films using Cp2Hf (CH3)2 precursor have been investigated. The calculations show that CH4 elimination reaction is energetically more favorable than CpH elimination reaction. As a result, the two ―CH3 ligands of Cp2Hf (CH3)2 may be dissociated prior to the two ―Cp rings. According to the activation barrier analysis, one CpH elimination may occurs sequentially following the first CH4 elimination reaction. During the pulse of Cp2Hf (CH3)2 precursor, the byproduct CH4 and a small amount of CpH are released.

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Initial Surface Reactions Mechanisms of Atomic Layer Deposition TiO2 on H/Si(100)-2×1 Surface

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.750-752.1052 ◽

2013 ◽

Vol 750-752 ◽

pp. 1052-1056 ◽

Cited By ~ 1

Author(s):

Guang Fen Zhou ◽

Jie Ren ◽

Shao Wen Zhang

Keyword(s):

Density Functional Theory ◽

Atomic Layer Deposition ◽

Adsorption Energy ◽

Reaction Mechanisms ◽

Density Functional ◽

Surface Reaction ◽

Atomic Layer ◽

Initial Surface ◽

Functional Theory ◽

Layer Deposition

The initial surface reaction mechanisms of atomic layer deposition TiO2on H/Si (100 )-2×1 surface using Ti (OCH3)4and H2O as precursors are investigated by density functional theory. The ALD process is divided into two half-reactions, i.e., Ti (OCH3)4and H2O half-reactions. The adsorption energy of Ti (OCH3)4on H/Si (100)2×1 surface is only-2.4 kJ/mol. The overall reaction of Ti (OCH3)4is exothermic, which indicates that Ti (OCH3)4half-reactions are favorable on thermodynamic. Howerver, H2O half-reactions are endothermic and thermodynamically unfavorable.

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Reaction Mechanism of Atomic Layer Deposition of Al on the Si (100) Surface: A Density Functional Theory Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.941-944.1283 ◽

2014 ◽

Vol 941-944 ◽

pp. 1283-1287

Author(s):

Mao Jin Dong ◽

Ran Fang ◽

Yu Qing Xiong ◽

Duo Shu Wang ◽

Ji Zhou Wang ◽

...

Keyword(s):

Density Functional ◽

Activation Barrier ◽

Exothermic Reaction ◽

Atomic Layer ◽

Reaction Process ◽

Chemical Adsorption ◽

Reaction Energy ◽

Functional Theory ◽

Barrier Energy ◽

Layer Deposition

Using H2 and Al (CH3)3(TMA) as precursor, we investigated the atomic layer deposition mechanism of the metal Al on Si (100) surface by density functional theory. The reaction process comprises two half-reaction depositions: TMA "half-reaction" includes I and II on the H blunt reaction surface; H2 "half-reaction" includes the subsequent reaction Ⅲ and Ⅳ. In the TMA half reaction process, trimethyl aluminum first molecularly adsorbed in the active site of H*-Si9H12-H* to form a stable complex in the form of chemical adsorption state. Potential curves show that at 298 K, adsorption energy is -2.26kJ/mol, with respect to the chemical adsorption state, the activation barrier energy is 124.72kJ/mol, and finally the whole exothermic reaction energy is 41.4kJ/mol. After H2 half reaction, the bond length between Al-Si can be considered equal; two Al-C bonds become relatively stable molecular structure. The adsorption energy is -0.10kJ/mol at 298 K, and the activation barrier energy 189.15kJ/mol. The results show that two half-reaction process mechanism is similar, TMA endothermic reaction needs more energy to be carried out under heating conditions ; endothermic and exothermic reaction energy is basic balance, the activation energy is large, so the reaction is the best using ionized gas to be carried out.

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First principles study of the atomic layer deposition of alumina by TMA–H2O-process

Physical Chemistry Chemical Physics ◽

10.1039/c5cp01912e ◽

2015 ◽

Vol 17 (26) ◽

pp. 17322-17334 ◽

Cited By ~ 47

Author(s):

Timo Weckman ◽

Kari Laasonen

Keyword(s):

Atomic Layer Deposition ◽

First Principles ◽

Reaction Mechanisms ◽

Density Functional ◽

Atomic Layer ◽

Functional Study ◽

Density Functional Study ◽

First Principles Study ◽

Layer Deposition

A comprehensive density functional study on the reaction mechanisms during the atomic layer deposition of alumina via trimethylaluminium–waterprocess.

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Initial Surface Reactions Mechanisms of Atomic Layer Deposition TiO2 Using Ti(OCH3)4 and H2O as Precursors

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.785-786.832 ◽

2013 ◽

Vol 785-786 ◽

pp. 832-836 ◽

Cited By ~ 1

Author(s):

Guang Fen Zhou ◽

Jie Ren ◽

Shao Wen Zhang

Keyword(s):

Density Functional Theory ◽

Atomic Layer Deposition ◽

Reaction Mechanisms ◽

Density Functional ◽

Surface Reaction ◽

Surface Reactions ◽

Atomic Layer ◽

Initial Surface ◽

Functional Theory ◽

Layer Deposition

The initial surface reaction mechanisms of atomic layer depositionTiO2using Ti (OCH3)4and H2O as the precursors are investigated by density functional theory. The ALD process is divided into two half-reactions, i.e., Ti (OCH3)4and H2O half-reactions. The adsorption of Ti (OCH3)4on OH/Si (100)2×1 surface is exothermic. However, the overall reaction of Ti (OCH3)4is endothermic. In addition, H2O half-reactions are endothermic and thermodynamically unfavorable.

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Atomic layer deposition of diisopropylaminosilane on WO3(001) and W(110): a density functional theory study

Physical Chemistry Chemical Physics ◽

10.1039/c6cp05720a ◽

2016 ◽

Vol 18 (42) ◽

pp. 29139-29146 ◽

Cited By ~ 2

Author(s):

Kyungtae Lee ◽

Woojin Lee ◽

Hyo Sug Lee ◽

Jaikwang Shin ◽

Jieun Park ◽

...

Keyword(s):

Density Functional Theory ◽

Reaction Mechanisms ◽

Density Functional ◽

Atomic Layer ◽

Dft Method ◽

Decomposition Reaction ◽

Density Functional Theory Study ◽

Functional Theory ◽

Layer Deposition ◽

The Density Functional Theory

The decomposition reaction mechanisms of the Si precursor, diisopropylaminosilane (DIPAS), on W(110) and WO3(001) surfaces are compared using the density functional theory (DFT) method.

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A Rare Low Spin Co(IV) Bis-Silyldiamide with High Thermal Stability: Exploring the Origin of an Unusual S = 1/2 Configuration

10.26434/chemrxiv.11691825.v2 ◽

2020 ◽

Author(s):

David Zanders ◽

Goran Bačić ◽

Dominique Leckie ◽

Oluwadamilola Odegbesan ◽

Jeremy M. Rawson ◽

...

Keyword(s):

Thermal Stability ◽

Density Functional ◽

Atomic Layer ◽

Epr Spectrum ◽

Functional Theory ◽

Cluster Calculations ◽

Layer Deposition ◽

Starting Point ◽

Higher Spin ◽

Surface Saturation

Attempted preparation of a chelated Co(II) β-silylamide re-sulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibits a room temperature magnetic moment of 1.8 B.M and a solid state axial EPR spectrum diagnostic of a rare S = 1/2 configuration. Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (–27 kcal/mol) over higher spin configurations for which density functional theory (DFT) showed no energetic preference. Unlike other Co(IV) complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in initial atomic layer deposition (ALD) surface saturation tests. The ease of synthesis and high-stability make 1 an attractive starting point to begin investigating otherwise inaccessible Co(IV) intermediates and synthesizing new materials.

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