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Kocevski V, Pilania G, Uberuaga BP. Modeling Disorder in Pyrochlores and Other Anion-Deficient Fluorite Structural Derivative Oxides. Front Chem 2021; 9:712543. [PMID: 34532309 PMCID: PMC8438134 DOI: 10.3389/fchem.2021.712543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 07/08/2021] [Indexed: 12/05/2022] Open
Abstract
Their very flexible chemistry gives oxide materials a richness in functionality and wide technological application. A specific group of oxides that have a structure related to fluorite but with less oxygen, termed anion-deficient fluorite structural derivatives and with pyrochlores being the most notable example, has been shown to exhibit a diversity of useful properties. For example, the possibility to undergo a transition from an ordered to disordered state allows these oxides to have high radiation tolerance. Atomistic-scale calculations in the form of molecular dynamics (MD) and density functional theory (DFT) have been extensively used to understand what drives this order/disorder transition. Here we give a brief overview of how atomistic-scale calculations are utilized in modeling disorder in pyrochlores and other anion-deficient fluorite structural derivatives. We discuss the modeling process from simple point defects to completely disordered structures, the dynamics during the disordering process, and the use of mathematical models to generate ordered solid-solution configurations. We also attempt to identify the challenges in modeling short range order and discuss future directions to more comprehensive models of the disordered structures.
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Affiliation(s)
- V Kocevski
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, United States
| | - G Pilania
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, United States
| | - B P Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, United States
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Agarwal S, Liedke MO, Jones ACL, Reed E, Kohnert AA, Uberuaga BP, Wang YQ, Cooper J, Kaoumi D, Li N, Auguste R, Hosemann P, Capolungo L, Edwards DJ, Butterling M, Hirschmann E, Wagner A, Selim FA. A new mechanism for void-cascade interaction from nondestructive depth-resolved atomic-scale measurements of ion irradiation-induced defects in Fe. Sci Adv 2020; 6:eaba8437. [PMID: 32832684 PMCID: PMC7439404 DOI: 10.1126/sciadv.aba8437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 06/16/2020] [Indexed: 06/11/2023]
Abstract
The nondestructive investigation of single vacancies and vacancy clusters in ion-irradiated samples requires a depth-resolved probe with atomic sensitivity to defects. The recent development of short-pulsed positron beams provides such a probe. Here, we combine depth-resolved Doppler broadening and positron annihilation lifetime spectroscopies to identify vacancy clusters in ion-irradiated Fe and measure their density as a function of depth. Despite large concentrations of dislocations and voids in the pristine samples, positron annihilation measurements uncovered the structure of vacancy clusters and the change in their size and density with irradiation dose. When combined with transmission electron microscopy measurements, the study demonstrates an association between the increase in the density of small vacancy clusters with irradiation and a remarkable reduction in the size of large voids. This, previously unknown, mechanism for the interaction of cascade damage with voids in ion-irradiated materials is a consequence of the high porosity of the initial microstructure.
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Affiliation(s)
- S Agarwal
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - M O Liedke
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - A C L Jones
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - E Reed
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - A A Kohnert
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - B P Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Y Q Wang
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - J Cooper
- Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27607, USA
| | - D Kaoumi
- Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27607, USA
| | - N Li
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - R Auguste
- Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - P Hosemann
- Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - L Capolungo
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - D J Edwards
- Nuclear Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - M Butterling
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - E Hirschmann
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - A Wagner
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - F A Selim
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
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Bergstrom ZJ, Li C, Samolyuk GD, Uberuaga BP, Wirth BD. Hydrogen interactions with low-index surface orientations of tungsten. J Phys Condens Matter 2019; 31:255002. [PMID: 30865943 DOI: 10.1088/1361-648x/ab0f6b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We report on density functional theory calculations that have been performed to systematically investigate the hydrogen-surface interaction as a function of surface orientation. The interactions that were analyzed include stable atomic adsorption sites, molecular hydrogen dissociation and absorption energies, migration pathways and barriers on tungsten surfaces, and the saturation coverage limits on the (1 1 1) surface. Stable hydrogen adsorption sites were found for all surfaces. For the reconstructed W(1 0 0), there are two primary adsorption sites: namely, the long-bridge and short-bridge sites. The threefold hollow site (3F) was found to be the most stable for W(1 1 0), while the bond-centered site between the first and second layer was found to be most stable for the W(1 1 1) surface. No bound adsorption sites for H2 molecules were found for the W surfaces. Hydrogen (H) migration on both the (1 0 0) and (1 1 0) surfaces is found to have preferred pathways for 1D motion, whereas the smallest migration barrier for net migration of H on the W(1 1 1) surface leads to 2D migration. Although weaker H interactions are predicted for the W(1 1 1) surface compared to the (1 0 0) or (1 1 0) surfaces, we observe higher H surface concentrations of Θ = 4.0 at zero K, possibly due to the corrugated surface structure. These results provide insight into H adsorption, surface saturation coverage and migration mechanisms necessary to describe the evolution from the dilute limit to concentrated coverages of H.
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Affiliation(s)
- Z J Bergstrom
- The University of Tennessee, Knoxville, TN, United States of America
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Pilania G, McClellan KJ, Stanek CR, Uberuaga BP. Physics-informed machine learning for inorganic scintillator discovery. J Chem Phys 2018; 148:241729. [DOI: 10.1063/1.5025819] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- G. Pilania
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - K. J. McClellan
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C. R. Stanek
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - B. P. Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Pilania G, Mannodi-Kanakkithodi A, Uberuaga BP, Ramprasad R, Gubernatis JE, Lookman T. Machine learning bandgaps of double perovskites. Sci Rep 2016; 6:19375. [PMID: 26783247 PMCID: PMC4726030 DOI: 10.1038/srep19375] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 12/07/2015] [Indexed: 01/28/2023] Open
Abstract
The ability to make rapid and accurate predictions on bandgaps of double perovskites is of much practical interest for a range of applications. While quantum mechanical computations for high-fidelity bandgaps are enormously computation-time intensive and thus impractical in high throughput studies, informatics-based statistical learning approaches can be a promising alternative. Here we demonstrate a systematic feature-engineering approach and a robust learning framework for efficient and accurate predictions of electronic bandgaps of double perovskites. After evaluating a set of more than 1.2 million features, we identify lowest occupied Kohn-Sham levels and elemental electronegativities of the constituent atomic species as the most crucial and relevant predictors. The developed models are validated and tested using the best practices of data science and further analyzed to rationalize their prediction performance.
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Affiliation(s)
- G Pilania
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos 87545, NM, USA
| | - A Mannodi-Kanakkithodi
- Department of Materials Science &Engineering and Institute of Materials Science, University of Connecticut, Storrs, 06269 CT USA
| | - B P Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos 87545, NM, USA
| | - R Ramprasad
- Department of Materials Science &Engineering and Institute of Materials Science, University of Connecticut, Storrs, 06269 CT USA
| | - J E Gubernatis
- Theoretical Division, Los Alamos National Laboratory, Los Alamos 87545, NM, USA
| | - T Lookman
- Theoretical Division, Los Alamos National Laboratory, Los Alamos 87545, NM, USA
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Gofryk K, Du S, Stanek CR, Lashley JC, Liu XY, Schulze RK, Smith JL, Safarik DJ, Byler DD, McClellan KJ, Uberuaga BP, Scott BL, Andersson DA. Anisotropic thermal conductivity in uranium dioxide. Nat Commun 2014; 5:4551. [DOI: 10.1038/ncomms5551] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 06/27/2014] [Indexed: 11/09/2022] Open
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Marks NA, Carter DJ, Sassi M, Rohl AL, Sickafus KE, Uberuaga BP, Stanek CR. Chemical evolution via beta decay: a case study in strontium-90. J Phys : Condens Matter 2013; 25:065504. [PMID: 23315221 DOI: 10.1088/0953-8984/25/6/065504] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using (90)Sr as a representative isotope, we present a framework for understanding beta decay within the solid state. We quantify three key physical and chemical principles, namely momentum-induced recoil during the decay event, defect creation due to physical displacement, and chemical evolution over time. A fourth effect, that of electronic excitation, is also discussed, but this is difficult to quantify and is strongly material dependent. The analysis is presented for the specific cases of SrTiO(3) and SrH(2). By comparing the recoil energy with available threshold displacement data we show that in many beta-decay situations defects such as Frenkel pairs will not be created during decay as the energy transfer is too low. This observation leads to the concept of chemical evolution over time, which we quantify using density functional theory. Using a combination of Bader analysis, phonon calculations and cohesive energy calculations, we show that beta decay leads to counter-intuitive behavior that has implications for nuclear waste storage and novel materials design.
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Affiliation(s)
- N A Marks
- Nanochemistry Research Institute, Curtin University, Perth, WA 6845, Australia.
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Mulroue J, Uberuaga BP, Duffy DM. Charge localization on the hexa-interstitial cluster in MgO. J Phys Condens Matter 2013; 25:065502. [PMID: 23307696 DOI: 10.1088/0953-8984/25/6/065502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Density functional theory was used to study the effects of charge localization on the structure and mobility of the highly mobile hexa-interstitial cluster in MgO. It was found that the relative stability of the configurations changed as charge was localized, with the higher energy intermediate configuration of the neutral cluster becoming the lowest energy configuration for the doubly charged cluster. The singly charged cluster was found to have the lowest migration barrier, with a barrier of 0.18 eV. The high mobility of the singly charged hexa-interstitial cluster could have a significant effect on microstructure evolution following radiation damage, while the detailed properties will be sensitive to the level of doping in the material.
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Affiliation(s)
- J Mulroue
- Department of Physics and Astronomy and the London Centre for Nanotechnology, University College London, London, UK
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Andersson DA, Espinosa-Faller FJ, Uberuaga BP, Conradson SD. Stability and migration of large oxygen clusters in UO2+x: Density functional theory calculations. J Chem Phys 2012; 136:234702. [DOI: 10.1063/1.4729842] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Li YH, Uberuaga BP, Jiang C, Choudhury S, Valdez JA, Patel MK, Won J, Wang YQ, Tang M, Safarik DJ, Byler DD, McClellan KJ, Usov IO, Hartmann T, Baldinozzi G, Sickafus KE. Role of antisite disorder on preamorphization swelling in titanate pyrochlores. Phys Rev Lett 2012; 108:195504. [PMID: 23003057 DOI: 10.1103/physrevlett.108.195504] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Indexed: 06/01/2023]
Abstract
Ion irradiation experiments and atomistic simulations were used to demonstrate that irradiation-induced lattice swelling in a complex oxide, Lu2Ti2O7, is due initially to the formation of cation antisite defects. X-ray diffraction revealed that cation antisite formation correlates directly with lattice swelling and indicates that the volume per antisite pair is approximately 12 Å3. First principles calculations revealed that lattice swelling is best explained by cation antisite defects. Temperature accelerated dynamics simulations indicate that cation Frenkel defects are metastable and decay to form antisite defects.
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Affiliation(s)
- Y H Li
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Abstract
The stabilities of selected fission products-Xe, Cs, and Sr-are investigated as a function of non-stoichiometry x in UO(2 ± x). In particular, density functional theory (DFT) is used to calculate the incorporation and solution energies of these fission products at the anion and cation vacancy sites, at the divacancy, and at the bound Schottky defect. In order to reproduce the correct insulating state of UO(2), the DFT calculations are performed using spin polarization and with the Hubbard U term. In general, higher charge defects are more soluble in the fuel matrix and the solubility of fission products increases as the hyperstoichiometry increases. The solubility of fission product oxides is also explored. Cs(2)O is observed as a second stable phase and SrO is found to be soluble in the UO(2) matrix for all stoichiometries. These observations mirror experimentally observed phenomena.
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Affiliation(s)
- P V Nerikar
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA. Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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Kittiratanawasin L, Smith R, Uberuaga BP, Sickafus KE. Radiation damage and evolution of radiation-induced defects in Er(2)O(3) bixbyite. J Phys Condens Matter 2009; 21:115403. [PMID: 21693918 DOI: 10.1088/0953-8984/21/11/115403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Collision cascade simulations were performed in the Er(2)O(3) sesquioxide. The resulting point defects observed at the end of the ballistic phase of the collision cascade were analysed and their evaluation over longer time examined using temperature accelerated dynamics and the kinetic Monte Carlo method. The result shows that the large mass difference between the Er and O atoms results in cascades with different structures where an initially energetic O atom can channel over long distances, depositing energy in smaller sub-regions, whereas denser cascades with vacancy-rich cores develop from Er primary knock-on atoms. The most mobile defect that can form is the isolated O vacancy but when this occurs as part of a larger defect cluster it becomes trapped. The energy barriers for all other defects to move are very high.
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Affiliation(s)
- L Kittiratanawasin
- Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK
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Uberuaga BP, Hoagland RG, Voter AF, Valone SM. Direct transformation of vacancy voids to stacking fault tetrahedra. Phys Rev Lett 2007; 99:135501. [PMID: 17930607 DOI: 10.1103/physrevlett.99.135501] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Indexed: 05/25/2023]
Abstract
Defect accumulation is the principal factor leading to the swelling and embrittlement of materials during irradiation. It is commonly assumed that, once defect clusters nucleate, their structure remains essentially constant while they grow in size. Here, we describe a new mechanism, discovered during accelerated molecular dynamics simulations of vacancy clusters in fcc metals, that involves the direct transformation of a vacancy void to a stacking fault tetrahedron (SFT) through a series of 3D structures. This mechanism is in contrast with the collapse to a 2D Frank loop which then transforms to an SFT. The kinetics of this mechanism are characterized by an extremely large rate prefactor, tens of orders of magnitude larger than is typical of atomic processes in fcc metals.
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Affiliation(s)
- B P Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Uberuaga BP, Smith R, Cleave AR, Montalenti F, Henkelman G, Grimes RW, Voter AF, Sickafus KE. Structure and mobility of defects formed from collision cascades in MgO. Phys Rev Lett 2004; 92:115505. [PMID: 15089149 DOI: 10.1103/physrevlett.92.115505] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Indexed: 05/24/2023]
Abstract
We study radiation-damage events in MgO on experimental time scales by augmenting molecular dynamics cascade simulations with temperature accelerated dynamics, molecular statics, and density functional theory. At 400 eV, vacancies and mono- and di-interstitials form, but often annihilate within milliseconds. At 2 and 5 keV, larger clusters can form and persist. While vacancies are immobile, interstitials aggregate into clusters (In) with surprising properties; e.g., an I4 is immobile, but an impinging I2 can create a metastable I6 that diffuses on the nanosecond time scale but is stable for years.
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Affiliation(s)
- B P Uberuaga
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Uberuaga BP, Leskovar M, Smith AP, Jonsson H, Olmstead M. Diffusion of Ge below the Si(100) surface: theory and experiment. Phys Rev Lett 2000; 84:2441-2444. [PMID: 11018905 DOI: 10.1103/physrevlett.84.2441] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/1999] [Indexed: 05/23/2023]
Abstract
We have studied diffusion of Ge into subsurface layers of Si(100). Auger electron diffraction measurements show Ge in the fourth layer after submonolayer growth at temperatures as low as 500 degrees C. Density functional theory predictions of equilibrium Ge subsurface distributions are consistent with the measurements. We identify a surprisingly low energy pathway resulting from low interstitial formation energy in the third and fourth layers. Doping significantly affects the formation energy, suggesting that n-type doping may lead to sharper Si/Ge interfaces.
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Affiliation(s)
- BP Uberuaga
- Department of Physics, Box 351560, University of Washington, Seattle, Washington 98195-1560 and Department of Chemistry, Box 351700, University of Washington, Seattle, Washington 98195-1700, USA
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