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Dynamic competition between island growth and coalescence in metal-on-insulator deposition
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-0908-7187
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-4811-478X
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-2864-9509
2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 16, p. 163107-1-163107-5Article in journal (Refereed) Published
Abstract [en]

The morphology of thin metal films and nanostructures synthesized from the vapor phase on insulating substrates is strongly influenced by the coalescence of islands. Here, we derive analytically the quantitative criterion for coalescence suppression by combining atomistic nucleation theory and a classical model of coalescence. Growth simulations show that using this criterion, a coalescence-free growth regime can be reached in which morphological evolution is solely determined by island nucleation, growth, and impingement. Experimental validation for the ability to control the rate of coalescence using this criterion and navigate between different growth regimes is provided by in situ monitoring of Ag deposition on SiO2. Our findings pave the way for creating thin films and nanostructures that exhibit a wide range of morphologies and physical attributes in a knowledge-based manner.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014. Vol. 105, no 16, p. 163107-1-163107-5
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-112133DOI: 10.1063/1.4900575ISI: 000344363000073OAI: oai:DiVA.org:liu-112133DiVA, id: diva2:763695
Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2018-01-11Bibliographically approved
In thesis
1. Dynamics of the Early Stages in Metal-on-Insulator Thin Film Deposition
Open this publication in new window or tab >>Dynamics of the Early Stages in Metal-on-Insulator Thin Film Deposition
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Thin films consist of nanoscale layers of material that are used in many technological applications to either functionalize a surface or serve as parts in miniaturized devices. The properties of a film are closely related to its microstructure, which in turn can be tuned during film preparation. Thin film growth involves a multitude of atomic-scale processes that cannot always be easily studied experimentally. Therefore, different types of computer simulations have been developed in order to test theoretical models of thin film growth in a highly controlled way. To be able to compare simulation and experimental results, the simulations must be able to model events on experimental time-scales, i.e. several seconds or minutes. This is achievable with the kinetic Monte Carlo method.

In this work, kinetic Monte Carlo simulations are used to model the initial growth stages of metal films on insulating, amorphous substrates. This includes the processes of island nucleation, three-dimensional island growth and island coalescence. Both continuous and pulsed vapor fluxes are investigated as deposition sources, and relations between deposition parameters and film morphology are formulated. Specifically, the film thickness at what is known as the “elongation transition” is studied as a function of the temporal profile of the vapor flux, adatom diffusivity and the coalescence rate. Since the elongation transition occurs due to hindrance of coalescence completion, two separate scaling behaviors of the elongation transition film thickness are found: one where coalescence occurs frequently and one where coalescence occurs infrequently. In the latter case, known nucleation behaviors can be used favorably to control the morphology of thin films, as these behaviors are not erased by island coalescence. Experimental results of Ag growth on amorphous SiO2 that confirm the existence of these two “growth regimes” are also presented for both pulsed and continuous deposition by magnetron sputtering. Knowledge of how to avoid coalescence for different deposition conditions allows nucleation for metal-on-insulator material systems to be studied and relevant physical quantities to be determined in a way not previously possible. This work also aids understanding of the growth evolution of polycrystalline films, which in conjunction with advanced deposition techniques allows thin films to be tailored to specific applications.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. p. 54
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1687
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112136 (URN)10.3384/lic.diva-112136 (DOI)978-91-7519-192-8 (ISBN)
Supervisors
Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2014-11-18Bibliographically approved
2. Nano- and mesoscale morphology evolution of metal films on weakly-interacting surfaces
Open this publication in new window or tab >>Nano- and mesoscale morphology evolution of metal films on weakly-interacting surfaces
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin films are structures consisting of one or several nanoscale atomic layers of material that are used to either functionalize a surface or constitute components in more complex devices. Many properties of a film are closely related to its microstructure, which allows films to be tailored to meet specific technological requirements. Atom-by-atom film growth from the vapor phase involves a multitude of atomic processes that may not be easily studied experimentally in real-time because they occur in small length- (≤ Å) and timescales (≤ ns). Therefore, different types of computer simulation methods have been developed in order to test theoretical models of thin film growth and unravel what experiments cannot show. In order to compare simulated and experimental results, the simulations must be able to model events on experimental time-scales, i.e. on the order of microseconds to seconds. This is achievable with the kinetic Monte Carlo (kMC) method.

In this work, the initial growth stages of metal deposition on weakly-interacting substrates is studied using both kMC simulations as well as experiments whereby growth was monitored using in situ probes. Such film/substrate material combinations are widely encountered in technological applications including low-emissivity window coatings to parts of microelectronics components. In the first part of this work, a kMC algorithm was developed to model the growth processes of island nucleation, growth and coalescence when these are functions of deposition parameters such as the vapor deposition rate and substrate temperature. The dynamic interplay between these growth processes was studied in terms of the scaling behavior of the film thickness at the elongation transition, for both continuous and pulsed deposition fluxes, and revealed in both cases two distinct growth regimes in which coalescence is either active or frozen out during deposition. These growth regimes were subsequently confirmed in growth experiments of Ag on SiO2, again for both pulsed and continuous deposition, by measuring the percolation thickness as well as the continuous film formation thickness. However, quantitative agreement with regards to scaling exponents in the two growth regimes was not found between simulations and experiments, and this prompted the development of a method to determine the elongation transition thickness experimentally. Using this method, the elongation transition of Ag on SiO2 was measured, with scaling exponents found in much better agreement with the simulation results. Further, these measurement data also allowed the calculation of surface properties such as the terrace diffusion barrier of Ag on SiO2 and the average island coalescence rate.

In the second part of this thesis, pioneering work is done to develop a fully atomistic, on-lattice model which describes the growth of Ag on weakly-interacting substrates. Simulations performed using this model revealed several key atomic-scale processes occurring at the film/substrate interface and on islands which govern island shape evolution, thereby contributing to a better understanding of how 3D island growth occurs at the atomic scale for a wide class of materials. The latter provides insights into the directed growth of metal nanostructures with controlled shapes on weakly-interacting substrates, including twodimensional crystals for use in catalytic and nano-electronic applications.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 68
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1835
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-144217 (URN)10.3384/diss.diva-144217 (DOI)9789176855706 (ISBN)
Public defence
2018-02-02, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Note

I den tryckta versionen saknades den populärvetenskapliga sammanfattningen på svenska. I den elektroniska versionen är den tillagd mellan Abstract (sida II) och Preface (sida III).

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-01-12Bibliographically approved

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Lü, BoElofsson, ViktorMünger, PeterSarakinos, Kostas

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