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Rönnby, K., Pedersen, H. & Ojamäe, L. (2023). On the limitations of thermal atomic layer deposition of InN using ammonia. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 41(2), Article ID 020401.
Open this publication in new window or tab >>On the limitations of thermal atomic layer deposition of InN using ammonia
2023 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 41, no 2, article id 020401Article in journal (Refereed) Published
Abstract [en]

Chemical vapor deposition of indium nitride (InN) is severely limited by the low thermal stability of the material, and, thus, low-temperature deposition processes such as atomic layer deposition (ALD) are needed to deposit InN films. The two chemically and structurally closely related materials—aluminum nitride and gallium nitride (GaN)—can be deposited by both plasma and thermal ALD, with ammonia (NH3) as a nitrogen precursor in thermal processes. InN, however, can only be deposited using plasma ALD, indicating that there might be a limitation to thermal ALD with NH3 for InN. We use quantum-chemical density functional theory calculations to compare the adsorption process of NH3 on GaN and InN to investigate if differences in the process could account for the lack of thermal ALD of InN. Our findings show a similar reactive adsorption mechanism on both materials, in which NH3 could adsorb onto a vacant site left by a desorbing methyl group from the surfaces. The difference in energy barrier for this adsorption indicates that the process is many magnitudes slower on InN compared to GaN. Slow kinetics would hinder NH3 from reactively adsorbing onto InN in the timeframe of the ALD growth process and, thus, limit the availability of a thermal ALD process.

Place, publisher, year, edition, pages
American Vacuum Society, 2023
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-191934 (URN)10.1116/6.0002355 (DOI)000936907900001 ()
Note

Funding agencies: This project was funded by the Swedish Foundation for Strategic Research through the project “Time-resolved low temperature CVD for III-nitrides” (No. SSF-RMA 15-0018). L.O. acknowledges financial support from the Swedish Research Council (VR). Supercomputing resources were provided by the Swedish National Infrastructure for Computing (SNIC) and the Swedish National Supercomputer Centre (NSC).

Available from: 2023-02-24 Created: 2023-02-24 Last updated: 2023-03-21Bibliographically approved
Samii, R., Fransson, A., Mpofu, P., Niiranen, P., Ojamäe, L., Kessler, V. & O´brien, N. (2022). Synthesis, Structure, and Thermal Properties of Volatile Group 11 Triazenides as Potential Precursors for Vapor Deposition. Inorganic Chemistry, 61(51), 20804-20813
Open this publication in new window or tab >>Synthesis, Structure, and Thermal Properties of Volatile Group 11 Triazenides as Potential Precursors for Vapor Deposition
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2022 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 61, no 51, p. 20804-20813Article in journal (Refereed) Published
Abstract [en]

Group 11 thin films are desirable as interconnects in microelectronics. Although many M-N-bonded Cu precursors have been explored for vapor deposition, there is currently a lack of suitable Ag and Au derivatives. Herein, we present monovalent Cu, Ag, and Au 1,3-di-tert-butyltriazenides that have potential for use in vapor deposition. Their thermal stability and volatility rival that of current state-of-the-art group 11 precursors with bidentate M-N-bonded ligands. Solution-state thermolysis of these triazenides yielded polycrystalline films of elemental Cu, Ag, and Au. The compounds are therefore highly promising as single-source precursors for vapor deposition of coinage metal films.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2022
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-190931 (URN)10.1021/acs.inorgchem.2c03071 (DOI)000898898000001 ()36516988 (PubMedID)
Note

Funding Agencies|Swedish foundation for Strategic Research [SSF-RMA 15-0018]; Knut and Alice Wallenberg foundation [KAW 2013.0049]; Swedish Research Council (VR); Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009 00971]

Available from: 2023-01-09 Created: 2023-01-09 Last updated: 2024-02-13Bibliographically approved
Damas, G., Rönnby, K., Pedersen, H. & Ojamäe, L. (2022). Understanding indium nitride thin film growth under ALD conditions by atomic scale modelling: From the bulk to the In-rich layer. Applied Surface Science, 592, Article ID 153290.
Open this publication in new window or tab >>Understanding indium nitride thin film growth under ALD conditions by atomic scale modelling: From the bulk to the In-rich layer
2022 (English)In: Applied Surface Science, ISSN 0169-4332, Vol. 592, article id 153290Article in journal (Refereed) Published
Abstract [en]

In recent decades, indium nitride (InN) has been attracting a great deal of attention for its potential applicability in the field of light-emitting diodes (LEDs) and high-frequency electronics. However, the contribution from adsorption- and reaction- related processes at the atomic scale level to the InN growth has not yet been unveiled, limiting the process optimization that is essential to achieve highly crystalline and pure thin films. In this report, we investigate the reaction pathways that are involved in the crystal growth of InN thin film in atomic layer deposition (ALD) techniques from trimethylindium (TMI) and ammonia (NH3) precursors. To accomplish this task, we use a solid-state approach to perform the ab-initio calculations within the Perdew–Burke–Ernzerhof functional (PBE) level of theory. The results clarify the activation role from the N-rich layer to decrease the barrier for the first TMI precursor dissociation from Δ‡H= +227 kJ/mol, in gas phase, to solely +16 kJ/mol, in the surface environment. In either case, the subsequent CH3 release is found to be thermo- and kinetically favored with methylindium (MI) formed at the hcp site and ethane (C2H6) as the byproduct. In the following step, the TMI physisorption at a nearby occupied hcp site promotes the sequential hydrogen removal from the N-rich layer at the minimum energy cost of Δ‡H < +105 kJ/mol with methane (CH4) release. An alternative mechanism involving the production of CH4 is also feasible upon dissociation in gas phase. Furthermore, the high concentration of CH3 radicals, from precursor dissociation, might be the origin of the carbon impurities in this material under the experimental conditions of interest. Finally, the passivation methodology is not found to affect the evaluation of the surface-related processes, whereas the inclusion of spin-polarization is demonstrated to be essential to the proper understanding of the reaction mechanism.

Place, publisher, year, edition, pages
Amsterdam, Netherlands: Elsevier, 2022
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-184437 (URN)10.1016/j.apsusc.2022.153290 (DOI)000793249200004 ()2-s2.0-85127669955 (Scopus ID)
Note

Funding: (SSF) through the project Time-Resolved Low temperature CVD [SSF-RMA 15-0018]; Swedish Research Council (VR)

Available from: 2022-04-20 Created: 2022-04-20 Last updated: 2022-05-23Bibliographically approved
Atakan, A., Erdtman, E., Mäkie, P., Ojamäe, L. & Odén, M. (2018). Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts. Journal of Catalysis, 362, 55-64
Open this publication in new window or tab >>Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
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2018 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, p. 55-64Article in journal (Refereed) Published
Abstract [en]

Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.

Keywords
Cu-Zr-SBA-15, CO2 hydrogenation, Catalysis, Time evolution, Thermodynamics, Methanol, Dimethyl ether
National Category
Nano Technology Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-147297 (URN)10.1016/j.jcat.2018.03.023 (DOI)000432770900007 ()
Note

Funding agencies: EUs Erasmus-Mundus program (The European School of Materials Doctoral Programme - DocMASE); Knut och Alice Wallenbergs Foundation [KAW 2012.0083]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Energy Agency [42022-1]

Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-06-14Bibliographically approved
Stenberg, P., Danielsson, Ö., Erdtman, E., Sukkaew, P., Ojamäe, L., Janzén, E. & Pedersen, H. (2017). Matching precursor kinetics to afford a more robust CVD chemistry: a case study of the C chemistry for silicon carbide using SiF4 as Si precursor. Journal of Materials Chemistry C, 5, 5818-5823
Open this publication in new window or tab >>Matching precursor kinetics to afford a more robust CVD chemistry: a case study of the C chemistry for silicon carbide using SiF4 as Si precursor
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2017 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, p. 5818-5823Article in journal (Refereed) Published
Abstract [en]

Chemical Vapor Deposition (CVD) is one of the technology platforms forming the backbone of the semiconductor industry and is vital in the production of electronic devices. To upscale a CVD process from the lab to the fab, large area uniformity and high run-to-run reproducibility are needed. We show by a combination of experiments and gas phase kinetics modeling that the combinations of Si and C precursors with the most well-matched gas phase chemistry kinetics gives the largest area of of homoepitaxial growth of SiC. Comparing CH4, C2H4 and C3H8 as carbon precursors to the SiF4 silicon precursor, CH4 with the slowest kinetics renders the most robust CVD chemistry with large area epitaxial growth and low temperature sensitivity. We further show by quantum chemical modeling how the surface chemistry is impeded by the presence of F in the system which limits the amount of available surface sites for the C to adsorb.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-137446 (URN)10.1039/c7tc00138j (DOI)000403571200024 ()
Note

Funding agencies: Knut & Alice Wallenberg Foundation (KAW) project Isotopic Control for Ultimate Material Properties; Swedish Foundation for Strategic Research project SiC - the Material for Energy-Saving Power Electronics [EM11-0034]; Swedish Government Strategic Research

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2018-10-08Bibliographically approved
Erdtman, E., Andersson, M., Lloyd Spetz, A. & Ojamäe, L. (2017). Simulations of the thermodynamics and kinetics of NH3 at the RuO2 (110) surface. Surface Science, 656, 77-85
Open this publication in new window or tab >>Simulations of the thermodynamics and kinetics of NH3 at the RuO2 (110) surface
2017 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 656, p. 9p. 77-85Article in journal (Refereed) Published
Abstract [en]

Ruthenium(IV)oxide (RuO2) is a material used for various purposes. It acts as a catalytic agent in several reactions, for example oxidation of carbon monoxide. Furthermore, it is used as gate material in gas sensors. In this work theoretical and computational studies were made on adsorbed molecules on RuO2 (110) surface, in order to follow the chemistry on the molecular level. Density functional theory calculations of the reactions on the surface have been performed. The calculated reaction and activation energies have been used as input for thermodynamic and kinetics calculations. A surface phase diagram was calculated, presenting the equilibrium composition of the surface at different temperature and gas compositions. The kinetics results are in line with the experimental studies of gas sensors, where water has been produced on the surface, and hydrogen is found at the surface which is responsible for the sensor response.

Place, publisher, year, edition, pages
Elsevier, 2017. p. 9
Keywords
Catalysis; Kinetics; Ruthenium dioxide; Sensor; Surface; Thermodynamics
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-133425 (URN)10.1016/j.susc.2016.10.006 (DOI)000390969300012 ()
Available from: 2016-12-28 Created: 2016-12-28 Last updated: 2018-11-26
Danielsson, Ö., Li, X., Ojamäe, L., Janzén, E., Pedersen, H. & Forsberg, U. (2016). A model for carbon incorporation from trimethyl gallium in chemical vapor deposition of gallium nitride. Journal of Materials Chemistry C, 4(4), 863-871
Open this publication in new window or tab >>A model for carbon incorporation from trimethyl gallium in chemical vapor deposition of gallium nitride
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2016 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 4, no 4, p. 863-871Article in journal (Refereed) Published
Abstract [en]

Gallium nitride (GaN) semiconductor material can become semi-insulating when doping with carbon. Semi-insulating buffer layers are utilized to prevent leakage currents in GaN high power devices. Carbon is inherently present during chemical vapor deposition (CVD) of GaN from the use of trimethyl gallium (TMGa) as precursor. TMGa decomposes in the gas phase, releasing its methyl groups, which could act as carbon source for doping. It is previously known that the carbon doping levels can be controlled by tuning the CVD process parameters, such as temperature, pressure and precursor flow rates. However, the mechanism for carbon incorporation from TMGa is not yet understood. In this paper, a model for predicting carbon incorporation from TMGa in GaN layers grown by CVD is proposed. The model is based on ab initio quantum chemical calculations of molecular adsorption and reaction energies. Using Computational Fluid Dynamics, with a chemical kinetic model for decomposition of the precursors and reactions in the gas phase, to calculate gas phase compositions at realistic process conditions, together with the proposed model, we obtain good correlations with measurements, for both carbon doping concentrations and growth rates, when varying the inlet NH3/TMGa ratio. When varying temperature (800 – 1050°C), the model overpredicts carbon doping concentrations at the lower temperatures, but predicts growth rates well, and the agreement with measured carbon doping concentrations is good above 1000°C.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Physical Sciences Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-118113 (URN)10.1039/c5tc03989d (DOI)000368839700027 ()
Note

Funding agencies: Swedish Foundation for Strategic Research (SSF); Swedish Defence Material Administration (FMV)

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Available from: 2015-05-22 Created: 2015-05-22 Last updated: 2021-07-06Bibliographically approved
Liu, Y. & Ojamäe, L. (2016). C-13 Chemical Shift in Natural Gas Hydrates from First-Principles Solid-State NMR Calculations. The Journal of Physical Chemistry C, 120(2), 1130-1136
Open this publication in new window or tab >>C-13 Chemical Shift in Natural Gas Hydrates from First-Principles Solid-State NMR Calculations
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 2, p. 1130-1136Article in journal (Refereed) Published
Abstract [en]

Natural gas hydrates (NGHs) are of interest both as a prospective energy resource and for possible technological applications. C-13 NMR technology is a powerful tool to characterize NGHs, and in this work, the trends and origins of C-13 NMR chemical shifts of hydrocarbon molecules in NGHs from quantum-chemical first-principles calculations on solid state phases are presented. The chemical shift is found to decrease as the size of the water cavities increases for single occupancy NGHs, and to increase as the amount of CH4 increases for the multioccupancy cases. In most cases, the chemical shift of NGHs monotonically increases as the external pressure increases. Furthermore, the chemical shift can be mainly attributed to the host-guest interaction together with a small contributions from water molecules for tight environments and mainly depends on host-guest interaction for loose environments. The theoretical results provide useful information for identification of the types of clathrate phases and guest molecules included in NGH samples taken from natural sites.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-125313 (URN)10.1021/acs.jpcc.5b11372 (DOI)000368754700035 ()
Note

Funding Agencies|Swedish Research Council (VR); Swedish Supercomputer Center (SNIC/NSC); China Scholarship Council [201206060016]

Available from: 2016-02-24 Created: 2016-02-19 Last updated: 2017-11-30
Andres Cisneros, G., Thor Wikfeldt, K., Ojamäe, L., Lu, J., Xu, Y., Torabifard, H., . . . Paesani, F. (2016). Modeling Molecular Interactions in Water: From Pairwise to Many Body Potential Energy Functions. Chemical Reviews, 116(13), 7501-7528
Open this publication in new window or tab >>Modeling Molecular Interactions in Water: From Pairwise to Many Body Potential Energy Functions
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2016 (English)In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, no 13, p. 7501-7528Article, review/survey (Refereed) Published
Abstract [en]

Almost 50 years have passed from the first computer simulations of water, and a large number of molecular models have been proposed since then to elucidate the unique behavior of water across different phases. In this article, we review the recent progress in the development of analytical potential energy functions that aim at correctly representing many-body effects. Starting from the many-body expansion of the interaction energy, specific focus is on different classes of potential energy functions built upon a hierarchy of approximations and on their ability to accurately reproduce reference data obtained from state-of-the-art electronic structure calculations and experimental measurements. We show that most recent potential energy functions, which include explicit short-range representations of two-body and three-body effects along with a physically correct description of many-body effects at all distances, predict the properties of water from the gas to the condensed phase with unprecedented accuracy, thus opening the door to the long-sought "universal model" capable of describing the behavior of water under different conditions and in different environments.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:liu:diva-130380 (URN)10.1021/acs.chemrev.5b00644 (DOI)000379794000003 ()27186804 (PubMedID)
Note

Funding Agencies|Royal Swedish Academy of Sciences through Nobel Institutes for Physics and Chemistry; Swedish Research Council; Department of Physics at Stockholm University; Icelandic Research Fund; Army Research Laboratory [W911NF-12-2-0023]; Cluster of Excellence RESOLV - Deutsche Forschungsgemeinschaft (DFG) [EXC 1069]; Leverhulme Early Career Fellowship [1441]; Isaac Newton Trust; Wayne State University; National Institutes of Health [R01GM108583]; National Science Foundation [CHE-1453204, ACI-1053575]; National Energy Research Scientific Computing Center (NERSCC); Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]

Available from: 2016-08-15 Created: 2016-08-05 Last updated: 2017-11-28
Sukkaew, P., Ojamäe, L., Kordina, O., Janzén, E. & Danielsson, Ö. (2016). Thermochemical Properties of Halides and Halohydrides of Silicon and Carbon. ECS Journal of Solid State Science and Technology, 5(2), P27-P35
Open this publication in new window or tab >>Thermochemical Properties of Halides and Halohydrides of Silicon and Carbon
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2016 (English)In: ECS Journal of Solid State Science and Technology, ISSN 2162-8769, E-ISSN 2162-8777, Vol. 5, no 2, p. P27-P35Article in journal (Refereed) Published
Abstract [en]

Atomization energies, enthalpies of formation, entropies as well as heat capacities of the SiHnXm and CHnXm systems, with X being F, Cl and Br, have been studied using quantum chemical calculations. The Gaussian-4 theory (G4) and Weizman-1 theory as modified by Barnes et al. 2009 (W1RO) have been applied in the calculations of the electronic, zero point and thermal energies. The effects of low-lying electronically excited states due to spin orbit coupling were included for all atoms and diatomic species by mean of the electronic partition functions derived from the experimental or computational energy splittings. The atomization energies, enthalpies of formation, entropies and heat capacities derived from both methods were observed to be reliable. The thermochemical properties in the temperature range of 298-2500 K are provided in the form of 7-coefficient NASA polynomials. (C) The Author(s) 2015. Published by ECS. All rights reserved.

Place, publisher, year, edition, pages
ELECTROCHEMICAL SOC INC, 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124117 (URN)10.1149/2.0081602jss (DOI)000365748800023 ()
Note

Funding Agencies|Swedish Foundation for Strategic Research

Available from: 2016-01-22 Created: 2016-01-19 Last updated: 2017-11-30
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5341-2637

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