Crystallization of amorphous complex oxides: New geometries and new compositions via solid phase epitaxy

Evans, Paul G.; Chen, Yajin; Tilka, Jack A.; Babcock, S.E.; Kuech, T. F.

doi:10.1016/j.cossms.2018.09.001

Cited by 25 publications

(24 citation statements)

References 138 publications

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“…As already mentioned, the observed recrystallization of amorphous PCMO resembles SPE of an amorphous Si which happens via a moving amorphous/crystalline interface, where velocities of a few nm per min requires elevated temperatures above 500 • C [33]. The recrystallization temperature can be significantly reduced to around 200-300 • C, if the recrystallization is assisted by ion irradiation [34]. Although the electron-beam induced recrystallization reported here also happens via the movement of the crystalline/amorphous interface, it however strongly differs from the SPE.…”

Section: Discussionmentioning

confidence: 67%

“…This will be discussed in detail further down. Thus, the process resembles the so-called solid phase epitaxial (SPE) growth, where an initially amorphous Si [33] or complex oxide [34] thin film is epitaxially recrystallized on a crystalline template at elevated temperatures. Remarkably, the electron-beam-induced SPE process in our environmental TEM study is observed at room temperature and depends on a reactive gas environment.…”

Section: Resultsmentioning

confidence: 99%

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In Situ Preparation of Pr1-xCaxMnO3 and La1-xSrxMnO3 Catalysts Surface for High-Resolution Environmental Transmission Electron Microscopy

2019

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The study of changes in the atomic structure of a catalyst under chemical reaction conditions is extremely important for understanding the mechanism of their operation. For in situ environmental transmission electron microscopy (ETEM) studies, this requires preparation of electron transparent ultrathin TEM lamella without surface damage. Here, thin films of Pr1-xCaxMnO3 (PCMO, x = 0.1, 0.33) and La1-xSrxMnO3 (LSMO, x = 0.4) perovskites are used to demonstrate a cross-section specimen preparation method, comprised of two steps. The first step is based on optimized focused ion beam cutting procedures using a photoresist protection layer, finally being removed by plasma-etching. The second step is applicable for materials susceptible to surface amorphization, where in situ recrystallization back to perovskite structure is achieved by using electron beam driven chemistry in gases. This requires reduction of residual water vapor in a TEM column. Depending on the gas environment, long crystalline facets having different atomic terminations and Mn-valence state, can be prepared.

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Section: Discussionmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

In Situ Preparation of Pr1-xCaxMnO3 and La1-xSrxMnO3 Catalysts Surface for High-Resolution Environmental Transmission Electron Microscopy

2019

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“…Amorphous oxide layers are not subjected to the constraints imposed by epitaxial synthesis, thereby creating novel pathways to synthesize hybrid functional materials on new substrates and with postassembly tunability of the geometry. [21] Here we show that SrTiO 3 /Si/Si 1−x Ge x NMs form rolledup tubes with sub-micrometer diameters that are determined by the large stresses arising from structural reconfiguration in the amorphous oxide. SrTiO 3 /Si/Si 1−x Ge x NMs roll up into micrometer-scale diameter tubes upon release from the growth substrate due to the elastic relaxation of stress from two sources: the epitaxial mismatch of Si 1−x Ge x and Si, and stress in the as-deposited amorphous SrTiO 3 .…”

Section: Introductionmentioning

confidence: 74%

“…Dramatic changes in the atomic configuration accompany interface formation, the relaxation of glassy states, and crystallization. [21,22] The bonding in amorphous form is incomplete yielding stress that varies during reconfiguration and relaxation. [23][24][25][26][27] Rolled-up NMs may serve as probes to measure film stress evolution during the structural transformation of complex oxides and provide insight into the fundamental mechanisms involved in such structural transformation.…”

Section: Introductionmentioning

confidence: 99%

Reconfiguration of Amorphous Complex Oxides: A Route to a Broad Range of Assembly Phenomena, Hybrid Materials, and Novel Functionalities

Prakash

Chen

Debasu

et al. 2021

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materials that are freestanding either at a stage in their fabrication, in their final state, or both. [1] NMs with thicknesses in the range of a few nanometers to a few hundred nanometers can be isolated from their substrates through synthesis and processing techniques that have become established in the last 20 years. [1][2][3][4][5] The lateral dimensions of NMs are at least two orders of magnitude larger than their thickness, making them a distinctive platform from 0D, 1D, and bulk materials. [6] NMs enable a vast range of possibilities, including i) the capability to subject materials to elastic strain fields with magnitudes or geometries that are not realizable in bulk materials or by direct growth; [7][8][9] ii) unique and rapid characterization of materials properties and kinetic processes; [10,11] iii) heterogeneous integration of materials via controlled transfer, including, into environments in which the NM materials would be otherwise inaccessible via synthesis; [12,13] iv) 3D structures that can be processed in parallel on large-area substrates and can find use in several applications. [14][15][16][17][18] The scope of applications and phenomena that benefit from NMs can be extended to a new spectrum of materials Reconfiguration of amorphous complex oxides provides a readily controllable source of stress that can be leveraged in nanoscale assembly to access a broad range of 3D geometries and hybrid materials. An amorphous SrTiO 3 layer on a Si:B/Si 1−x Ge x :B heterostructure is reconfigured at the atomic scale upon heating, exhibiting a change in volume of ≈2% and accompanying biaxial stress. The Si:B/Si 1−x Ge x :B bilayer is fabricated by molecular beam epitaxy, followed by sputter deposition of SrTiO 3 at room temperature. The processes yield a hybrid oxide/semiconductor nanomembrane. Upon release from the substrate, the nanomembrane rolls up and has a curvature determined by the stress in the epitaxially grown Si:B/Si 1−x Ge x :B heterostructure. Heating to 600 °C leads to a decrease of the radius of curvature consistent with the development of a large compressive biaxial stress during the reconfiguration of SrTiO 3 . The control of stresses via post-deposition processing provides a new route to the assembly of complex-oxide-based heterostructures in 3D geometry. The reconfiguration of metastable mechanical stressors enables i) synthesis of various types of strained superlattice structures that cannot be fabricated by direct growth and ii) technologies based on strain engineering of complex oxides via highly scalable lithographic processes and on large-area semiconductor substrates.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202105424.

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“…[ 9–14 ] On one hand, crystallization of complex oxides, in general, has associated kinetic barriers from the slow diffusion in solids. [ 15 ] When there are two metal cations involved in crystallization of complex oxides like ABO 3 , their nonuniform distribution can result in spontaneous phase separation to form simple oxides. [ 16 ] A delicate balance of their sol–gel rates and the precautious control of thermal annealing procedure is needed.…”

Section: Introductionmentioning

confidence: 99%

Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response

Liu

Shi

et al. 2020

Adv Funct Materials

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A colloidal-amphiphile-templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane-containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO 3 as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO . Those novel materials make it possible to build up correlations between mesoscale porosity and surfacesensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO 3 , there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.complex oxides, in general, has associated kinetic barriers from the slow diffusion in solids. [15] When there are two metal cations involved in crystallization of complex oxides like ABO 3 , their nonuniform distribution can result in spontaneous phase separation to form simple oxides. [16] A delicate balance of their sol-gel rates and the precautious control of thermal annealing procedure is needed. On the other hand, ordering competition between the crystallization of oxides and the mesoscale porosity brings profound difficulties to synthesize complex oxides (e.g., perovskites and ilmenites) with mesoporous structures. Crystallization usually leads to the formation of large crystalline grains that will create strong interfacial energies between crystalline walls and pores (e.g., air or templates). For any templated growth of mesoporous oxides using hydrocarbon-based surfactants or block copolymers (BCPs) as soft templates, [17][18][19] mesoscale nanostructures collapse prior to the crystallization of oxides, [20][21][22] because these soft templates are not mechanically strong and thermally stable under elevated temperatures (i.e., >500 °C).Nanostructures show a profound impact on the magnetic properties of materials as well and a few theoretical models have been proposed to understand magnetic behavior of nanoscale particles. [23][24][25][26][27][28][29][30] The magnetic ordering temperature (Curie temperature or Néel temperature) in magnetic materials

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Crystallization of amorphous complex oxides: New geometries and new compositions via solid phase epitaxy

Cited by 25 publications

References 138 publications

In Situ Preparation of Pr1-xCaxMnO3 and La1-xSrxMnO3 Catalysts Surface for High-Resolution Environmental Transmission Electron Microscopy

In Situ Preparation of Pr1-xCaxMnO3 and La1-xSrxMnO3 Catalysts Surface for High-Resolution Environmental Transmission Electron Microscopy

Reconfiguration of Amorphous Complex Oxides: A Route to a Broad Range of Assembly Phenomena, Hybrid Materials, and Novel Functionalities

Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response

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