Substrate Surface Structure Effects on Microstructure of Epitaxial Films PDF Download
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Author:
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Category :
Languages : en
Pages : 5
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages : 5
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Microstructure of epitaxial thin films grown on sapphire substrates using the metal organic chemical vapor deposition technique were found to depend on the substrates surface structure. Epitaxial TiO2 films grown on the sapphire (0001) substrates were highly-oriented polycrystal and the films on the (1120) substrates were single crystal. First-principles total energy calculations were carried out to gain atomistic understandings of sapphire surface structures and their effects on microstructure of epitaxial films. The surface terminating atom planes were found to be Al atoms for the (0001) surface and O atoms for the (1120). Minimum step heights were one sixth of the lattice constant c for the (0001) and one half of the lattice constant a for the (1120). Steps of minimum height or its odd multiples on sapphire (0001) surface double the number of variants in the deposited films. The symmetry and step of the substrate surface and symmetry of the epitaxial growth plane controlled the microstructure of the epitaxial films.
Author: Harry A. Atwater
Publisher: Mrs Proceedings
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 784
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The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.
Author:
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Category : Aeronautics
Languages : en
Pages : 702
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Author: Jie He
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages :
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This work was motivated and focused on the growth mechanism, microstructures and interfaces of barium titanate, BaTiO3 (BTO), based epitaxial thin films. Transimission electron microscopy (TEM), high resolution TEM (HRTEM), electron diffraction (ED) have been mainly employed in this study for microstructure investigations of BTO-based epitaxial thin films with the assistance of other materials characterization methods, such as X-ray diffraction (XRD), atomic force microscopy (AFM), Nanoindentation testing, etc. As a basic studying model, epitaxial BTO films were first deposited on the (001) MgO substrate using RF magnetron sputtering to provide fundamental knowledge of the film growth for BTO based thin films. The epitaxial BTO films show a tetragonal crystal structure (a = 4.02 Å and c = 4.11 Å) with epitaxial nanodomains induced from the rough film/substrate interface due to the modification of the substrate surface characteristics (steps, terraces, and kinks) during the deposition process. Two new phases of - calculus [gamma]y (Ba10TiO26) and Hß (BaTi8O24) were formed on the MgO substrate using RF magnetron sputtering. The atomic structures of the two new phases were determined and examined. The [gamma]y phase has a monoclinic structure, Cm, a=16.49 Å̊̊, b=8.94 Å, c=3.94 Å, y=77°. The Hß phase has a monoclinic structure, Cm, a = 17.88̊Å̊, b = 7.21Å, c = 3.94 Å̊̊̊, y =82°. Both [gamma]y and Hß phases have four different oriented domains. The orientation relationship between domains and MgO substrate is discussed. Initail study shows that these new phases possess novel and interesting properties. The doped BTO films with different dopant (Sr2 and Zr4) fabricated using pulsed laser deposition (PLD) have been studied for doping effects, interface effects and film growth mechanism. The (Ba, Sr)TiO3 (BST) epitaxial films grown on 1.2° and 5.3° miscut substrates consist of lager commensurate domains, and correspondly show higher dielectric constant and dielectric tunability, and lower average modulus and hardness than those of the films grown on the 3.5° miscut substrate. The results suggest that the differences on the interfacial structure have a tremendous effect on the properties of the films. The investigation on epitaxial Ba(Zr, Ti)O3 (BZT) and 2% Mn doped Ba(Zr, Ti)O3 (Mn:BZT) thin films grown on MgO substrate revealed the formation of twin-coupled domains on the epilayer by sharing their {111}/{110} planes as common planes. The structure evolution from epilayer to nanopillars is accomplished by alternatively introducing {111} and {110} twin boundaries, resulting in gradual shrinking or enlarging of the lateral size of the epitaxial grains/twin coupled nanopillars. The formations of twin domains, sharing planes and structure transition mechasim have been discussed in detail. Eventually, the microstructures and layer interfaces of [Mn:BZT//Mn:BST]N multilayer films consisting of 2% Mn doped (Ba, Sr)TiO3 (Mn:BST) and Mn:BZT layers on MgO (001) substrates with various deposition rates, deposition period numbers N were studied to provide an integral view of the formation of multilayer films in BTO system. All the [Mn:BZT//Mn:BST]N multilayer films present epitaxial quality and induced {111}/{110} twin-coupled domains initially formed at different film thickness/layers. The film/substrate interface has an important role for the formation of twin domains and the proportion of twin domain structures in the entire films. The layer interfaces between Mn:BST and Mn:BZT with period compression and extension strains were observed and discussed. The microstructure evolution and structure-related nano-mechanical properties of the multilayer films have been systematically investigated.
Author: Adriana Eleni Lita
Publisher:
ISBN:
Category :
Languages : en
Pages : 408
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Author: Polly Wanda Chu
Publisher:
ISBN:
Category :
Languages : en
Pages : 434
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Thin titanium dioxide films were produced by metalorganic chemical vapor deposition on sapphire(0001) in an ultrahigh vacuum (UHV) chamber. A method was developed for producing controlled submonolayer depositions from titanium isopropoxide precursor. Film thickness ranged from 0.1 to 2.7 nm. In situ X-ray photoelectron spectroscopy (XPS) was used to determine film stoichiometry with increasing thickness. The effect of isothermal annealing on desorption was evaluated. Photoelectron peak shapes and positions from the initial monolayers were analyzed for evidence of interface reaction. Deposition from titanium isopropoxide is divided into two regimes: depositions below and above the pyrolysis temperature. This temperature was determined to be 300 deg C. Controlled submonolayers of titanium oxide were produced by cycles of dosing with titanium isopropoxide vapor below and annealing above 300 deg C. Precursor adsorption below the pyrolysis temperature was observed to saturate after 15 minutes of dosing. The quantity absorbed was shown to have an upper limit of one monolayer. The stoichiometry of thin films grown by the cycling method were determined to be TiO2. Titanium dioxide film stoichiometry was unaffected by isothermal annealing at 700 deg C. Annealing produced a decrease in film thickness. This was explained as due to desorption. Desorption ceased at approximately 2.5 to 3 monolayers, suggesting bonding of the initial monolayers of film to sapphire is stronger than to itself. Evidence of sapphire reduction at the interface by the depositions was not observed. The XPS O is peak shifted with increased film thickness. The shifts were consistent with oxygen in sapphire and titanium dioxide having different O is photoelectron peak positions. Simulations showed the total shifts for thin films ranging in thickness of 0.1 to 2.7 nm to be -0.99 to -1.23 eV. Thick films were produced for comparison.
Author: Viktor Elofsson
Publisher: Linköping University Electronic Press
ISBN: 9176856399
Category :
Languages : en
Pages : 92
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Thin film growth from the vapor phase has for a long time intrigued researchers endeavouring to unravel and understand atomistic surface processes that govern film formation. Their motivation has not been purely scientific, but also driven by numerous applications where this understanding is paramount to knowledge-based design of novel film materials with tailored properties. Within the above framework, this thesis investigates growth of metal films on weakly bonding substrates, a combination of great relevance for applications concerning e.g., catalysis, graphene metallization and architectural glazing. When metal vapor condenses on weakly bonding substrates three dimensional islands nucleate, grow and coalesce prior to forming a continuous film. The combined effect of these initial growth stages on film formation and morphology evolution is studied using pulsed vapor fluxes for the model system Ag/SiO2. It is shown that the competition between island growth and coalescence completion determines structure evolution. The effect of the initial growth stages on film formation is also examined for the tilted columnar microstructure obtained when vapor arrives at an angle that deviates from the substrate surface normal. This is done using two metals with distinctly different nucleation behaviour, and the findings suggest that the column tilt angle is set by nucleation conditions in conjunction with shadowing of the vapor flux by adjacent islands. Vapor arriving at an angle can in addition result in films that exhibit preferred crystallographic orientations, both out-of-plane and in-plane. Their emergence is commonly described by an evolutionary growth model, which for some materials predict a double in-plane alignment that has not been observed experimentally. Here, an experiment is designed to replicate the model’s growth conditions, confirming the existence of double in-plane alignment. New and added film functionalities can further be unlocked by alloying. Properties are then largely set by chemistry and atomic arrangement, where the latter can be affected by thermodynamics, kinetics and vapor flux modulation. Their combined effect on atomic arrangement is here unravelled by presenting a research methodology that encompasses high resolution vapor flux modulation, nanoscale structure v vi probes and growth simulations. The methodology is deployed to study the immiscible Ag-Cu and miscible Ag-Au model systems, for which it is shown that capping of Cu by Ag atoms via near surface diffusion processes and rough morphology of the Ag-Au growth front are the decisive structure forming processes in each respective system. The results generated in this thesis are of relevance for tuning structure of metal films grown on weakly bonding substrates. They also indicate that improved growth models are required to accurately describe structure evolution and emergence of a preferred in-plane orientation in films where vapor arrives at an angle that deviates from the substrate surface normal. In addition, this thesis presents a methodology that can be used to identify and understand structure forming processes in multicomponent films, which may enable tailoring of atomic arrangement and related properties in technologically relevant material systems.
Author: K. N. Tu
Publisher: Elsevier
ISBN: 1483218295
Category : Technology & Engineering
Languages : en
Pages : 351
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Book Description
Treatise on Materials Science and Technology, Volume 24: Preparation and Properties of Thin Films covers the progress made in the preparation of thin films and the corresponding study of their properties. The book discusses the preparation and property correlations in thin film; the variation of microstructure of thin films; and the molecular beam epitaxy of superlattices in thin film. The text also describes the epitaxial growth of silicon structures (thermal-, laser-, and electron-beam-induced); the characterization of grain boundaries in bicrystalline thin films; and the mechanical properties of thin films on substrates. The ion beam modification of thin film; the use of thin alloy films for metallization in microelectronic devices; and the fabrication and physical properties of ultrasmall structures are also encompassed. Materials scientists and materials engineers will find the book invaluable.
Author: J. Dumas
Publisher: Elsevier
ISBN: 0444596542
Category : Technology & Engineering
Languages : en
Pages : 763
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Book Description
A wide range of progress in materials development [single crystals, ceramics, thin films, wire and tapes] is reported in the 169 papers in this volume. The main focus of the papers is in attaining a better understanding of the relationship between microstructure and electrical properties. Invited papers cover topics such as the effects of substitution and doping; multilayers; nanostructure characterisation; electric field effects in High Tc Superconductors [HTS]; surface stability; critical currents; flux pinning and magnetooptic imaging of flux patterns; effects of irradiation induced defects; properties and preparation of materials; microwave properties and electronic devices. A clearly broadened basis for understanding processes and mechanisms in [HTS] is portrayed. Appreciable progress has been achieved in the reproducible manufacturing of high quality materials supported by very efficient methods in microstructural analysis. This essential improvement is reflected in the increased number of practical devices encouraging the use of HTS in applications for electronics and power engineering, all of which are reviewed in depth in this work.
