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BETA
Sangiovanni, Davide GiuseppeORCID iD iconorcid.org/0000-0002-1379-6656
Alternative names
Publications (10 of 27) Show all publications
Jamnig, A., Sangiovanni, D. G., Abadias, G. & Sarakinos, K. (2019). Atomic-scale diffusion rates during growth of thin metal films on weakly-interacting substrates. Scientific Reports, 9, Article ID 6640.
Open this publication in new window or tab >>Atomic-scale diffusion rates during growth of thin metal films on weakly-interacting substrates
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 6640Article in journal (Refereed) Published
Abstract [en]

We use a combined experimental and theoretical approach to study the rates of surface diffusion processes that govern early stages of thin Ag and Cu film morphological evolution on weakly-interacting amorphous carbon substrates. Films are deposited by magnetron sputtering, at temperatures T-S between 298 and 413 K, and vapor arrival rates F in the range 0.08 to 5.38 monolayers/s. By employing in situ and real-time sheet-resistance and wafer-curvature measurements, we determine the nominal film thickness Theta at percolation (Theta(perc)) and continuous film formation (Theta(cont)) transition. Subsequently, we use the scaling behavior of Theta(perc) and Theta(cont) as a function of F and T-s, to estimate, experimentally, the temperature-dependent diffusivity on the substrate surface, from which we calculate Ag and Cu surface migration energy barriers E-D(exp) and attempt frequencies nu(exp)(0). By critically comparing E-D(exp) and nu(exp)(0) with literature data, as well as with results from our ab initio molecular dynamics simulations for single Ag and Cu adatom diffusion on graphite surfaces, we suggest that: (i) E-D(exp) and nu(exp)(0) correspond to diffusion of multiatomic clusters, rather than to diffusion of monomers; and (ii) the mean size of mobile clusters during Ag growth is larger compared to that of Cu. The overall results of this work pave the way for studying growth dynamics in a wide range of technologically-relevant weakly-interacting film/substrate systems-including metals on 2D materials and oxides-which are building blocks in next-generation nanoelectronic, optoelectronic, and catalytic devices.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-158369 (URN)10.1038/s41598-019-43107-8 (DOI)000466127100065 ()31036908 (PubMedID)2-s2.0-85065068804 (Scopus ID)
Note

Funding Agencies|French Government program "Investissements dAvenir" (LABEX INTERACTIFS) [ANR-11-LABX-0017-01]; Linkoping University ("LiU Career Contract") [Dnr-LiU-2015-01510]; Swedish research council [VR-2015-04630]; Olle Engkvist foundation [SOEB 190-312]; Olle Engkvist Foundation

Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-11-05Bibliographically approved
Almyras, G., Sangiovanni, D. G. & Sarakinos, K. (2019). Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System. Materials, 12(2), Article ID 215.
Open this publication in new window or tab >>Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 2, article id 215Article in journal (Refereed) Published
Abstract [en]

We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1-xAlxN (0 x 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the models predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of approximate to 40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1-xAlxN (0 amp;lt; x amp;lt; 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
titanium-aluminum nitride; Ti-Al-N; MD simulations; molecular dynamics; interatomic potential; MEAM; force-field model; spinodal decomposition; phase stability
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:liu:diva-155607 (URN)10.3390/ma12020215 (DOI)000459719000019 ()30634593 (PubMedID)
Note

Funding Agencies|Olle Engkvist foundation; competence center FunMat-II - Vinnova [2016-05156]; Linkoping University ("LiU Career Contract") [LiU-2015-01510]; Swedish research council [VR-2015-04630]; Olle Engkvist foundation [SOEB 190-312]

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-06-28
Sangiovanni, D. G., Kostov Gueorguiev, G. & Kakanakova-Georgieva, A. (2018). Ab initio molecular dynamics of atomic-scale surface reactions: insights into metal organic chemical vapor deposition of AlN on graphene. Physical Chemistry, Chemical Physics - PCCP, 20(26), 17751-17761
Open this publication in new window or tab >>Ab initio molecular dynamics of atomic-scale surface reactions: insights into metal organic chemical vapor deposition of AlN on graphene
2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 26, p. 17751-17761Article in journal (Refereed) Published
Abstract [en]

Metal organic chemical vapor deposition (MOCVD) of group III nitrides on graphene heterostructures offers new opportunities for the development of flexible optoelectronic devices and for the stabilization of conceptually-new two-dimensional materials. However, the MOCVD of group III nitrides is regulated by an intricate interplay of gas-phase and surface reactions that are beyond the resolution of experimental techniques. We use density-functional ab initio molecular dynamics (AIMD) with van der Waals corrections to identify atomistic pathways and associated electronic mechanisms driving precursor/surface reactions during metal organic vapor phase epitaxy at elevated temperatures of aluminum nitride on graphene, considered here as model case study. The results presented provide plausible interpretations of atomistic and electronic processes responsible for delivery of Al, C adatoms, and C-Al, CHx, AlNH2 admolecules on pristine graphene via precursor/surface reactions. In addition, the simulations reveal C adatom permeation across defect-free graphene, as well as exchange of C monomers with graphene carbon atoms, for which we obtain rates of approximate to 0.3 THz at typical experimental temperatures (1500 K), and extract activation energies Eexca = 0.28 +/- 0.13 eV and attempt frequencies A(exc) = 2.1 (x1.7(+/- 1)) THz via Arrhenius linear regression. The results demonstrate that AIMD simulations enable understanding complex precursor/surface reaction mechanisms, and thus propose AIMD to become an indispensable routine prediction-tool toward more effective exploitation of chemical precursors and better control of MOCVD processes during synthesis of functional materials.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-149847 (URN)10.1039/c8cp02786b (DOI)000437473300021 ()29915819 (PubMedID)
Note

Funding Agencies|Swedish Research Council (VR) through FLAG-ERA JTC project GRIFONE [VR 2015-06816, VR 2017-04071]; Olle Engkvist Foundation

Available from: 2018-08-02 Created: 2018-08-02 Last updated: 2019-06-28
Sangiovanni, D. G. (2018). Copper adatom, admolecule transport, and island nucleation on TiN(0 0 1) via ab initio molecular dynamics. Applied Surface Science, 50, 180-189
Open this publication in new window or tab >>Copper adatom, admolecule transport, and island nucleation on TiN(0 0 1) via ab initio molecular dynamics
2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 50, p. 180-189Article in journal (Refereed) Published
Abstract [en]

Density-functional ab initio molecular dynamics (AIMD) simulations are carried out to determine Cu adatom and admolecule transport properties as a function of temperature, as well as atomistic processes leading to formation of Cu/TiN(0 0 1) islands at 350 K. At very low temperatures T ≤ 200 K, Cu adatoms (Cuad) migrate among favored fourfold-hollow surface sites by passing across atop-Ti metastable positions. For increasing temperatures, however, Cuad transport becomes progressively more isotropic, and switches continuously from normal- to super-diffusive with mean-square displacement dependencies on time that alternate between linear and exponential. Despite that, the Cuad diffusivity D can be expressed by a fairly Arrhenius-like behavior D(T) = 8.26(×2±1) × 10−4 cm2 s−1exp[(−0.04 ± 0.01 eV)/(kBT)] over the entire investigated temperature range (100 ≤ T ≤ 1000 K). AIMD simulations also reveal that the condensation of Cu adatoms into Cux>1 adspecies is kinetically hindered by long-range (>5.5 Å) adatom/adatom repulsion. During Cu island nucleation, all Cu atoms occupy atop-N positions indicating favored Cu(0 0 1)/TiN(0 0 1) epitaxial growth. Nevertheless, Cu agglomerates formed by five, or more, atoms tend to arrange in 3D structures, which maximize intracluster bonds while minimizing film/substrate interactions. Results here presented provide insights for understanding the properties of weakly-interacting metal/substrate interface systems in general.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Chemical Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-148576 (URN)10.1016/j.apsusc.2018.04.191 (DOI)000433199000021 ()
Note

Funding agencies: Olle Engkvist Foundation

Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2019-06-28
Sangiovanni, D., Mei, A. B., Hultman, L., Chirita, V., Petrov, I. & Greene, J. E. (2016). Ab Initio Molecular Dynamics Simulations of Nitrogen/VN(001) Surface Reactions: Vacancy-Catalyzed N-2 Dissociative Chemisorption, N Adatom Migration, and N-2 Desorption. The Journal of Physical Chemistry C, 120(23), 12503-12516
Open this publication in new window or tab >>Ab Initio Molecular Dynamics Simulations of Nitrogen/VN(001) Surface Reactions: Vacancy-Catalyzed N-2 Dissociative Chemisorption, N Adatom Migration, and N-2 Desorption
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 23, p. 12503-12516Article in journal (Refereed) Published
Abstract [en]

We use density-functional ab initio molecular dynamics to investigate the kinetics of N/VN(001) surface reactions at temperatures ranging from 1600 to 2300 K. N adatoms (N-ad) on VN(001) favor epitaxial atop-V positions and diffuse among them by transiting through 4-fold hollow (FFH) sites, at which they are surrounded by two V and two N surface atoms. After several atop-V -amp;gt; FFH -amp;gt; atop-V jumps, isolated N adatoms bond strongly with an underlying N surface (N-surf) atom. Frequent N-ad/N-surf pair exchange reactions lead to N-2 desorption, which results in the formation of an anion surface vacancy. N vacancies rapidly migrate via in-plane (110) jumps and act as efficient catalysts for the dissociative chemisorption of incident N-2 molecules. During exposure of VN(001) to incident atomic N gas atoms, N-ad/N-ad recombination and desorption is never observed, despite a continuously high N monomer surface coverage. Instead, N-2 desorption is always initiated by a N adatom removing a N surface atom or by energetic N gas atoms colliding with N-ad or N-surf atoms. Similarities and differences between: N/VN(001) vs. previous N/TiN(001) results, discussed on the basis of temperature-dependent ab initio electronic structures and chemical bonding, provide insights for controlling the reactivity of NaCl-structure transition-metal nitride (001) surfaces via electron-concentration tuning.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-130283 (URN)10.1021/acs.jpcc.6b02652 (DOI)000378196200021 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation (Isotope Project) [2011.0094]; Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2014-5790, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials (through Swedens innovation agency VINNOVA) [MatLiU 2009-00971]

Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2019-06-28
Sangiovanni, D., Hultman, L., Chirita, V., Petrov, I. & Greene, J. E. (2016). Effects of phase stability, lattice ordering, and electron density on plastic deformation in cubic TiWN pseudobinary transition-metal nitride alloys. Acta Materialia, 103, 823-835
Open this publication in new window or tab >>Effects of phase stability, lattice ordering, and electron density on plastic deformation in cubic TiWN pseudobinary transition-metal nitride alloys
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 103, p. 823-835Article in journal (Refereed) Published
Abstract [en]

We carry out density functional theory calculations to compare the energetics of layer glide, as well as stress vs. strain curves, for cubic Ti0.5W0.5N pseudobinary alloys and reference B1-structure TiN. Irrespective of the degree of ordering on the metal sublattice, the hardness and stiffness of Ti0.5W0.5, as estimated by stress strain results and resistance to layer glide, are comparable to that of the parent binary TiN, while ductility is considerably enhanced. After an initial elastic response to an applied load, the pseudobinary alloy deforms plastically, thus releasing accumulated mechanical stress. In contrast, stress continues to increase linearly with strain in TiN. Layer glide in Ti0.5W0.5N is promoted by a high valence-electron concentration which enables the formation of strong metallic bonds within the slip direction upon deformation. [1111-oriented Ti0.5W0.5N layers characterized by high local metal-sublattice ordering exhibit low resistance to slip along < 110 > directions due to energetically favored formation of (111) hexagonal stacking faults. This is consistent with the positive formation energy of < 111 >-ordered Tio.5W0.5N with respect to mixing of cubic-BI TiN and hexagonal WC-structure WN. In the cubic pseudobinary alloy, slip occurs parallel, as well as orthogonal, to the resolved applied stress at the interface between layers with the lowest friction. We suggest that analogous structural metastability (mixing cubic and hexagonal TM nitride binary phases) and electronic (high valence electron concentration) effects are responsible for the enhanced toughness recently demonstrated experimentally for cubic single-crystal pseudobinary V0.5W0.5N and V0.5MocoN epitaxial layers. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Nitrides; Toughness Phase stability; Density functional theory (DFT); Electronic structure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-124462 (URN)10.1016/j.actamat.2015.10.039 (DOI)000367630500081 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2011.0094]; Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2014-5790, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials through Swedens innovation agency VINNOVA [2009-00971]

Available from: 2016-02-02 Created: 2016-02-01 Last updated: 2019-06-28
Sangiovanni, D., Hellman, O., Alling, B. & Abrikosov, I. (2016). Efficient and accurate determination of lattice-vacancy diffusion coefficients via non equilibrium ab initio molecular dynamics. PHYSICAL REVIEW B, 93(9), 094305
Open this publication in new window or tab >>Efficient and accurate determination of lattice-vacancy diffusion coefficients via non equilibrium ab initio molecular dynamics
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 9, p. 094305-Article in journal (Refereed) Published
Abstract [en]

We revisit the color-diffusion algorithm [Aeberhard et al., Phys. Rev. Lett. 108, 095901 (2012)] in non equilibrium ab initio molecular dynamics (NE-AIMD) and propose a simple efficient approach for the estimation of monovacancy jump rates in crystalline solids at temperatures well below melting. Color-diffusion applied to monovacancy migration entails that one lattice atom (colored atom) is accelerated toward the neighboring defect site by an external constant force F. Considering bcc molybdenum between 1000 and 2800 K as a model system, NE-AIMD results show that the colored-atom jump rate k(NE) increases exponentially with the force intensity F, up to F values far beyond the linear-fitting regime employed previously. Using a simple model, we derive an analytical expression which reproduces the observed k(NE)(F) dependence on F. Equilibrium rates extrapolated by NE-AIMD results are in excellent agreement with those of unconstrained dynamics. The gain in computational efficiency achieved with our approach increases rapidly with decreasing temperatures and reaches a factor of 4 orders of magnitude at the lowest temperature considered in the present study.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127268 (URN)10.1103/PhysRevB.93.094305 (DOI)000372711200003 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2011.0094]; Swedish Research Council (VR) [621-2011-4417, 2015-04391, 637-2013-7296, 330-2014-336]; Linkoping Linnaeus Initiative LiLi-NFM [2008-6572]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials [MatLiU 2009-00971]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Tomsk State University Academic D. I. Mendeleev Fund Program

Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2019-06-28
Edström, D., Sangiovanni, D., Hultman, L., Petrov, I., Greene, J. E. & Chirita, V. (2016). Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 34(4), 041509-1-041509-9
Open this publication in new window or tab >>Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth
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2016 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 34, no 4, p. 041509-1-041509-9Article in journal (Refereed) Published
Abstract [en]

Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200K are carried out using incident flux ratios N/Ti -1, 2, and 4. The films are analyzed as a function of composition, island size distribution, island edge orientation, and vacancy formation. Results show that N/Ti-1 films are globally understoichiometric with dispersed Ti-rich surface regions which serve as traps to nucleate 111-oriented islands, leading to local epitaxial breakdown. Films grown with N/Ti=2 are approximately stoichiometric and the growth mode is closer to layer-by-layer, while N/Ti-4 films are stoichiometric with N-rich surfaces. As N/Ti is increased from 1 to 4, island edges are increasingly polar, i. e., 110-oriented, and N-terminated to accommodate the excess N flux, some of which is lost by reflection of incident N atoms. N vacancies are produced in the surface layer during film deposition with N/Ti-1 due to the formation and subsequent desorption of N-2 molecules composed of a N adatom and a N surface atom, as well as itinerant Ti adatoms pulling up N surface atoms. The N vacancy concentration is significantly reduced as N/Ti is increased to 2; with N/Ti-4, Ti vacancies dominate. Overall, our results show that an insufficient N/Ti ratio leads to surface roughening via nucleation of small dispersed 111 islands, whereas high N/Ti ratios result in surface roughening due to more rapid upper-layer nucleation and mound formation. The growth mode of N/Ti-2 films, which have smoother surfaces, is closer to layer-by-layer. (C) 2016 American Vacuum Society.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-130405 (URN)10.1116/1.4953404 (DOI)000379588000027 ()
Note

Funding Agencies|Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2009-00971, 2013-4018, 2014-5790]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials; Knut and Alice Wallenberg Foundation (Isotope Project)

Available from: 2016-08-15 Created: 2016-08-05 Last updated: 2019-06-28
Sangiovanni, D., Tasnadi, F., Hultman, L., Petrov, I., Greene, J. E. & Chirita, V. (2016). N and Ti adatom dynamics on stoichiometric polar TiN(111) surfaces. Surface Science, 649, 72-79
Open this publication in new window or tab >>N and Ti adatom dynamics on stoichiometric polar TiN(111) surfaces
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2016 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 649, p. 72-79Article in journal (Refereed) Published
Abstract [en]

We use molecular dynamics (MD) based on the modified embedded atom method (MEAM) to determine diffusion coefficients and migration pathways for Ti and N adatoms (Ti-ad and N-ad) on TiN(111). The reliability of the classical model-potential is verified by comparison with density functional theory (DFT) results at 0 K. MD simulations carried out at temperatures between 600 and 1800 K show that both Ti-ad and N-ad favor fcc surface sites and migrate among them by passing through metastable hcp positions. We find that N-ad species are considerably more mobile than Ti-ad on TiN(111); contrary to our previous results on TiN(001). In addition, we show that lattice vibrations at finite temperatures strongly modify the potential energy landscape and result in smaller adatom migration energies, E-a = 1.03 for Ti-ad and 0.61 eV for N-ad, compared to 0 K values E-aOK = 1.55 (Ti-ad) and 0.79 eV (N-ad). We also demonstrate that the inclusion of dipole corrections, neglected in previous DFT calculations, is necessary in order to obtain the correct formation energies for polar surfaces such as TiN(111). (C) 2016 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2016
Keywords
Surface diffusion; Nitrides; Molecular dynamics; Density functional theory; Polar surfaces
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:liu:diva-130423 (URN)10.1016/j.susc.2016.01.031 (DOI)000379097000012 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2011.0094]; Swedish Research Council (VR) [2014-5790]; Linkoping Linnaeus Initiative LiLi-NFM [2008-6572]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials through Swedens innovation agency VINNOVA [MatLiU 2009-00971]

Available from: 2016-08-07 Created: 2016-08-05 Last updated: 2019-06-28
Mei, A. B., Hellman, O., Wireklint, N., Schlepuetz, C. M., Sangiovanni, D., Alling, B., . . . Greene, J. E. (2015). Dynamic and structural stability of cubic vanadium nitride. Physical Review B. Condensed Matter and Materials Physics, 91(5), 054101
Open this publication in new window or tab >>Dynamic and structural stability of cubic vanadium nitride
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2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 5, p. 054101-Article in journal (Refereed) Published
Abstract [en]

Structural phase transitions in epitaxial stoichiometric VN/MgO(011) thin films are investigated using temperature-dependent synchrotron x-ray diffraction (XRD), selected-area electron diffraction (SAED), resistivity measurements, high-resolution cross-sectional transmission electron microscopy, and ab initio molecular dynamics (AIMD). At room temperature, VN has the B1 NaCl structure. However, below T-c = 250 K, XRD and SAED results reveal forbidden (00l) reflections of mixed parity associated with a noncentrosymmetric tetragonal structure. The intensities of the forbidden reflections increase with decreasing temperature following the scaling behavior I proportional to (T-c - T)(1/2). Resistivity measurements between 300 and 4 K consist of two linear regimes resulting from different electron/phonon coupling strengths in the cubic and tetragonal-VN phases. The VN transport Eliashberg spectral function alpha F-2(tr)(h omega), the product of the phonon density of states F(h omega) and the transport electron/phonon coupling strength alpha(2)(tr)(h omega), is determined and used in combination with AIMD renormalized phonon dispersion relations to show that anharmonic vibrations stabilize the NaCl structure at T greater than T-c. Free-energy contributions due to vibrational entropy, often neglected in theoretical modeling, are essential for understanding the room-temperature stability of NaCl-structure VN, and of strongly anharmonic systems in general.

Place, publisher, year, edition, pages
American Physical Society, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-114566 (URN)10.1103/PhysRevB.91.054101 (DOI)000348872600001 ()
Note

Funding Agencies|Swedish Research Council (VR) program [637-2013-7296, 2014-5790, 2009-00971, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science [SFO Mat-LiU 2009-00971]; DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]

Available from: 2015-03-02 Created: 2015-02-26 Last updated: 2019-06-28
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1379-6656

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