Growth mechanisms of ceria- and zirconia-based epitaxial thin films and hetero-structures grown by pulsed laser deposition

Pergolesi, Daniele; Fronzi, Marco; Fabbri, Emiliana; Tebano, A.; Traversa, Enrico

doi:10.1007/s40243-012-0006-6

Cited by 21 publications

(17 citation statements)

References 29 publications

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“…Instead, RHEED revealed a three-dimensional growth mode, also known as island or layer-plus-island growth mode. Such a growth mechanism along the (001) crystallographic orientation of ceria films has been reported and explained 29 . This growth mode facilitates the nucleation of dislocations 12 13 , which assist the strain relaxation.…”

Section: Resultsmentioning

confidence: 87%

In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

et al. 2016

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Many properties of materials can be changed by varying the interatomic distances in the crystal lattice by applying stress. Ideal model systems for investigations are heteroepitaxial thin films where lattice distortions can be induced by the crystallographic mismatch with the substrate. Here we describe an in situ simultaneous diagnostic of growth mode and stress during pulsed laser deposition of oxide thin films. The stress state and evolution up to the relaxation onset are monitored during the growth of oxygen ion conducting Ce0.85Sm0.15O2-δ thin films via optical wafer curvature measurements. Increasing tensile stress lowers the activation energy for charge transport and a thorough characterization of stress and morphology allows quantifying this effect using samples with the conductive properties of single crystals. The combined in situ application of optical deflectometry and electron diffraction provides an invaluable tool for strain engineering in Materials Science to fabricate novel devices with intriguing functionalities.

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Section: Resultsmentioning

confidence: 87%

In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

et al. 2016

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“…In this film, the likelihood of dislocation nucleation is reduced due to the small lattice mismatch, which leads to small local distortions between islands. The island growth mode in SDC is also likely not driven by strain but results because the (111) facets of SDC have a lower surface energy than the (001) facets [52].…”

Section: Stress Relaxation and Growth Mechanismmentioning

confidence: 99%

Stress generation and evolution in oxide heteroepitaxy

et al. 2018

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Many physical properties of oxides can be changed by inducing lattice distortions in the crystal through heteroepitaxial growth of thin films. The average lattice strain can often be tuned by changing the film thickness or using suitable buffer layers between film and substrate. The exploitation of the full potential of strain engineering for sample or device fabrication rests on the understanding of the fundamental mechanisms of stress generation and evolution. For this study an optical measurement of the substrate curvature is used to monitor in situ how the stress builds up and relaxes during the growth of oxide thin films by pulsed laser deposition. The relaxation behavior is correlated with the growth mode, which is monitored simultaneously with reflection high-energy electron diffraction. The stress relaxation data is fitted and compared with theoretical models for stress evolution which were established for semiconductor epitaxy. The initial stage of the growth appears to be governed by surface stress and surface energy effects, while the subsequent stress relaxation is found to be fundamentally different between films grown on single-crystal substrates and on buffer layers. The first case can be rationalized with established theoretical models, but these models fail in the attempt to describe the growth on buffer layers. This is most probably due to the larger average density of crystalline defects in the buffer layers, which leads to a two-step stress relaxation mechanism, driven first by the nucleation and later by the migration of dislocation lines.

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“…51,92 Mismatch induced coherency strain can be reduced by introduction of misfit dislocations but also by tilting of the interface planes. This may be the cause why any strain effect is supressed (despite of 5.2 % misfit) and why the authors observe no conductivity effect.…”

Section: Experimental Studies On Ysz Multilayers From Literaturementioning

confidence: 99%

Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes – an improved model for nanocrystalline thin films and a review of experimental data

Korte

Keppner

Peters

et al. 2014

Phys. Chem. Chem. Phys.

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A phenomenological and analytical model for the influence of strain effects on atomic transport in columnar thin films is presented. A model system consisting of two types of crystalline thin films with coherent interfaces is assumed. Biaxial mechanical strain ε0 is caused by lattice misfit of the two phases. The conjoined films consist of columnar crystallites with a small diameter l. Strain relaxation by local elastic deformation, parallel to the hetero-interface, is possible along the columnar grain boundaries. The spatial extent δ0 of the strained hetero-interface regions can be calculated, assuming an exponential decay of the deformation-forces. The effect of the strain field on the local ionic transport in a thin film is then calculated by using the thermodynamic relation between (isostatic) pressure and free activation enthalpy ΔG(#). An expression describing the total ionic transport relative to bulk transport of a thin film or a multilayer as a function of the layer thickness is obtained as an integral average over strained and unstrained regions. The expression depends only on known material constants such as Young modulus Y, Poisson ratio ν and activation volume ΔV(#), which can be combined as dimensionless parameters. The model is successfully used to describe own experimental data from conductivity and diffusion studies. In the second part of the paper a comprehensive literature overview of experimental studies on (fast) ion transport in thin films and multilayers along solid-solid hetero-interfaces is presented. By comparing and reviewing the data the observed interface effects can be classified into three groups: (i) transport along interfaces between extrinsic ionic conductors (and insulator), (ii) transport along an open surface of an extrinsic ionic conductor and (iii) transport along interfaces between intrinsic ionic conductors. The observed effects in these groups differ by about five orders of magnitude in a very consistent way. The modified interface transport in group (i) is most probably caused by strain effects, misfit dislocations or disordered transition regions.

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Growth mechanisms of ceria- and zirconia-based epitaxial thin films and hetero-structures grown by pulsed laser deposition

Cited by 21 publications

References 29 publications

In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

Stress generation and evolution in oxide heteroepitaxy

Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes – an improved model for nanocrystalline thin films and a review of experimental data

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