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Sivakumar S, Zwier E, Meisenheimer PB, Heron JT. Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides. J Vis Exp 2018. [PMID: 29912185 DOI: 10.3791/57746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.
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Affiliation(s)
- Sai Sivakumar
- Department of Materials Science and Engineering, University of Michigan
| | - Elizabeth Zwier
- Department of Materials Science and Engineering, University of Michigan
| | | | - John T Heron
- Department of Materials Science and Engineering, University of Michigan;
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Joress H, Brock JD, Woll AR. Quick X-ray reflectivity using monochromatic synchrotron radiation for time-resolved applications. JOURNAL OF SYNCHROTRON RADIATION 2018; 25:706-716. [PMID: 29714180 PMCID: PMC5929355 DOI: 10.1107/s1600577518003004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/20/2018] [Indexed: 06/08/2023]
Abstract
A new technique for the parallel collection of X-ray reflectivity (XRR) data, compatible with monochromatic synchrotron radiation and flat substrates, is described and applied to the in situ observation of thin-film growth. The method employs a polycapillary X-ray optic to produce a converging fan of radiation, incident onto a sample surface, and an area detector to simultaneously collect the XRR signal over an angular range matching that of the incident fan. Factors determining the range and instrumental resolution of the technique in reciprocal space, in addition to the signal-to-background ratio, are described in detail. This particular implementation records ∼5° in 2θ and resolves Kiessig fringes from samples with layer thicknesses ranging from 3 to 76 nm. The value of this approach is illustrated by showing in situ XRR data obtained with 100 ms time resolution during the growth of epitaxial La0.7Sr0.3MnO3 on SrTiO3 by pulsed laser deposition at the Cornell High Energy Synchrotron Source (CHESS). Compared with prior methods for parallel XRR data collection, this is the first method that is both sample-independent and compatible with the highly collimated, monochromatic radiation typical of third-generation synchrotron sources. Further, this technique can be readily adapted for use with laboratory-based sources.
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Affiliation(s)
- H. Joress
- Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, USA
- Materials Science and Engineering Department, Cornell University, Ithaca, NY, USA
| | - J. D. Brock
- Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, USA
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - A. R. Woll
- Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, USA
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Gianfrancesco AG, Tselev A, Baddorf AP, Kalinin SV, Vasudevan RK. The Ehrlich-Schwoebel barrier on an oxide surface: a combined Monte-Carlo and in situ scanning tunneling microscopy approach. NANOTECHNOLOGY 2015; 26:455705. [PMID: 26489518 DOI: 10.1088/0957-4484/26/45/455705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The controlled growth of epitaxial films of complex oxides requires an atomistic understanding of key parameters determining final film morphology, such as termination dependence on adatom diffusion, and height of the Ehrlich-Schwoebel (ES) barrier. Here, through an in situ scanning tunneling microscopy study of mixed-terminated La5/8Ca3/8MnO3 (LCMO) films, we image adatoms and observe pile-up at island edges. Image analysis allows determination of the population of adatoms at the edge of islands and fractions on A-site and B-site terminations. A simple Monte-Carlo model, simulating the random walk of adatoms on a sinusoidal potential landscape using Boltzmann statistics is used to reproduce the experimental data, and provides an estimate of the ES barrier as ∼0.18 ± 0.04 eV at T = 1023 K, similar to those of metal adatoms on metallic surfaces. These studies highlight the utility of in situ imaging, in combination with basic Monte-Carlo methods, in elucidating the factors which control the final film growth in complex oxides.
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Affiliation(s)
- Anthony G Gianfrancesco
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831, USA. ORNL Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge TN 37831, USA. UT/ORNL Bredesen Center, University of Tennessee, Knoxville, TN, USA
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Ferguson JD, Kim Y, Kourkoutis LF, Vodnick A, Woll AR, Muller DA, Brock JD. Epitaxial oxygen getter for a brownmillerite phase transformation in manganite films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:1226-1230. [PMID: 21381119 DOI: 10.1002/adma.201003581] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 11/09/2010] [Indexed: 05/30/2023]
Affiliation(s)
- J D Ferguson
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
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Ferguson JD, Arikan G, Dale DS, Woll AR, Brock JD. Measurements of surface diffusivity and coarsening during pulsed laser deposition. PHYSICAL REVIEW LETTERS 2009; 103:256103. [PMID: 20366266 DOI: 10.1103/physrevlett.103.256103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Indexed: 05/29/2023]
Abstract
Pulsed laser deposition (PLD) of homoepitaxial SrTiO(3) 001 was studied with in situ x-ray specular reflectivity and surface diffuse x-ray scattering. Unlike prior reflectivity-based studies, these measurements access both time and length scales of the evolution of the surface morphology during growth. In particular, we show that this technique allows direct measurements of the diffusivity for both inter- and intralayer transport. Our results explicitly limit the possible role of island breakup, demonstrate the key roles played by nucleation and coarsening in PLD, and place an upper bound on the Ehrlich-Schwoebel barrier for downhill interlayer diffusion.
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Affiliation(s)
- J D Ferguson
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
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Dale D, Suzuki Y, Brock JD. In situ x-ray reflectivity studies of dynamics and morphology during heteroepitaxial complex oxide thin film growth. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:264008. [PMID: 21694342 DOI: 10.1088/0953-8984/20/26/264008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a method, based on refraction effects in continuous, stratified media, for quantitative analysis of specular x-ray reflectivity from interfaces with atomic-scale roughness. Roughness at interfaces has previously been incorporated into this framework via Fourier transform of a continuous height distribution, but this approach breaks down when roughness approaches the atomic scale and manifests discrete character. By modeling the overall roughness at interfaces as a convolution of discrete and continuous height distributions, we have extended the applicability of this reflectivity model to atomic-scale roughness. The parameterization of thickness and roughness enables quantitative analysis of time-resolved in situ reflectivity studies of thin film growth, modeling step-flow, layer-by-layer and three-dimensional growth within a single framework. We present the application of this model to the analysis of anti-Bragg growth oscillations measured in situ during heteroepitaxial growth of La(0.7)Sr(0.3)MnO(3) on [Formula: see text] SrTiO(3) at different temperatures and pressures, and discuss the evolution of surface morphology.
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Affiliation(s)
- Darren Dale
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA. Cornell Center for Materials Research, Cornell University, Ithaca, NY 14853, USA
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Christen HM, Eres G. Recent advances in pulsed-laser deposition of complex oxides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:264005. [PMID: 21694339 DOI: 10.1088/0953-8984/20/26/264005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Pulsed-laser deposition (PLD) is one of the most promising techniques for the formation of complex-oxide heterostructures, superlattices, and well controlled interfaces. The first part of this paper presents a review of several useful modifications of the process, including methods inspired by combinatorial approaches. We then discuss detailed growth kinetics results, which illustrate that 'true' layer-by-layer (LBL) growth can only be approached, not fully met, even though many characterization techniques reveal interfaces with unexpected sharpness. Time-resolved surface x-ray diffraction measurements show that crystallization and the majority of interlayer mass transport occur on timescales that are comparable to those of the plume/substrate interaction, providing direct experimental evidence that a growth regime exists in which non-thermal processes dominate PLD. This understanding shows how kinetic growth manipulation can bring PLD closer to ideal LBL than any other growth method available today.
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Affiliation(s)
- H M Christen
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Vonk V, Driessen KJI, Huijben M, Rijnders G, Blank DHA, Rogalla H, Harkema S, Graafsma H. Initial structure and growth dynamics of YBa(2)Cu(3)O(7-delta) during pulsed laser deposition. PHYSICAL REVIEW LETTERS 2007; 99:196106. [PMID: 18233090 DOI: 10.1103/physrevlett.99.196106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Indexed: 05/25/2023]
Abstract
The initial heteroepitaxial growth of YBa{2}Cu{3}O{7-delta} films on SrTiO3(001) substrates during pulsed laser deposition shows a growth-mode transition and a change of growth unit. The growth starts with two blocks, each two-thirds the size of the complete unit cell. The first of these blocks grows in a step-flow fashion, whereas the second grows in the layer-by-layer mode. Subsequent deposition occurs layer-by-layer of complete unit cells. These results suggest that the surface diffusion in the heteroepitaxial case is strongly influenced by the competition with formation energies, which is important for the fabrication of heteroepitaxial devices on the unit cell scale.
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Affiliation(s)
- V Vonk
- Faculty of Science and Technology, MESA+ Research Institute, University of Twente, 7500 AE, Enschede, The Netherlands.
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Lee YR, Gray A, Tischler J, Czoschke P, Hong H, Chang SL, Chiang TC. Quantum oscillations and beats in X-ray diffraction during film growth. PHYSICAL REVIEW LETTERS 2007; 99:156103. [PMID: 17995191 DOI: 10.1103/physrevlett.99.156103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2007] [Indexed: 05/25/2023]
Abstract
X-ray diffraction from a growing film at an anti-Bragg point should exhibit bilayer oscillations caused by interference. In an experiment of TiN film growth by laser ablation onto sapphire, an unexpected beating envelope function is found to modulate the oscillations. The successive nodes and antinodes are identified with the development of new growth domains separated by one atomic layer in thickness. This effect allows atomic layer counting of the film thickness distribution. The results imply that the growth is not characterized by a continuum stochastic process, as usually assumed.
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Affiliation(s)
- Y-R Lee
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
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Tischler JZ, Eres G, Larson BC, Rouleau CM, Zschack P, Lowndes DH. Nonequilibrium interlayer transport in pulsed laser deposition. PHYSICAL REVIEW LETTERS 2006; 96:226104. [PMID: 16803326 DOI: 10.1103/physrevlett.96.226104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Indexed: 05/10/2023]
Abstract
We use time-resolved surface x-ray diffraction measurements with microsecond range resolution to study the growth kinetics of pulsed laser deposited . Time-dependent surface coverages corresponding to single laser shots were determined directly from crystal truncation rod intensity transients. Analysis of surface coverage evolution shows that extremely fast nonequilibrium interlayer transport, which occurs concurrently with the arrival of the laser plume, dominates the deposition process. A much smaller fraction of material, which is governed by the dwell time between successive laser shots, is transferred by slow, thermally driven interlayer transport processes.
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Affiliation(s)
- J Z Tischler
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Willmott PR, Herger R, Schlepütz CM, Martoccia D, Patterson BD. Energetic surface smoothing of complex metal-oxide thin films. PHYSICAL REVIEW LETTERS 2006; 96:176102. [PMID: 16712314 DOI: 10.1103/physrevlett.96.176102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Indexed: 05/09/2023]
Abstract
A novel energetic smoothing mechanism in the growth of complex metal-oxide thin films is reported from in situ kinetic studies of pulsed laser deposition of on , using x-ray reflectivity. Below 50% monolayer coverage, prompt insertion of energetic impinging species into small-diameter islands causes them to break up to form daughter islands. This smoothing mechanism therefore inhibits the formation of large-diameter 2D islands and the seeding of 3D growth. Above 50% coverage, islands begin to coalesce and their breakup is thereby suppressed. The energy of the incident flux is instead rechanneled into enhanced surface diffusion, which leads to an increase in the effective surface temperature of DeltaT approximately 500 K. These results have important implications on optimal conditions for nanoscale device fabrication using these materials.
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Affiliation(s)
- P R Willmott
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
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Fleet A, Dale D, Woll AR, Suzuki Y, Brock JD. Multiple time scales in diffraction measurements of diffusive surface relaxation. PHYSICAL REVIEW LETTERS 2006; 96:055508. [PMID: 16486952 DOI: 10.1103/physrevlett.96.055508] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Indexed: 05/06/2023]
Abstract
We grew SrTiO3 on SrTiO3(001) by pulsed laser deposition, using x-ray scattering to monitor the growth in real time. The time-resolved small-angle scattering exhibits a well-defined length scale associated with the spacing between unit-cell high surface features. This length scale imposes a discrete spectrum of Fourier components and rate constants upon the diffusion equation solution, evident in multiple exponential relaxation of the "anti-Bragg" diffracted intensity. An Arrhenius analysis of measured rate constants confirms that they originate from a single activation energy.
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Affiliation(s)
- Aaron Fleet
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
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