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Phonon Thermal Conductivity of Scandium Nitride for Thermoelectrics from Rst- Principles Calculations and Thin-Lm Growth

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Phonon Thermal Conductivity of Scandium Nitride for Thermoelectrics from Rst- Principles Calculations and Thin-Lm Growth View metadata,Downloaded citation and from similar orbit.dtu.dk papers on:at core.ac.uk Dec 20, 2017 brought to you by CORE provided by Online Research Database In Technology Phonon thermal conductivity of scandium nitride for thermoelectrics from rst- principles calculations and thin-lm growth Kerdsongpanya, Sit; Hellman, Olle ; Sun, Bo ; Koh, Yee Kan ; Lu, Jun; Van Nong, Ngo; Simak, Sergei I. ; Alling, Björn ; Eklund, Per Published in: Physical Review B Link to article, DOI: 10.1103/PhysRevB.96.195417 Publication date: 2017 Document Version Peer reviewed version Link back to DTU Orbit Citation (APA): Kerdsongpanya, S., Hellman, O., Sun, B., Koh, Y. K., Lu, J., Van Nong, N., ... Eklund, P. (2017). Phonon thermal conductivity of scandium nitride for thermoelectrics from rst-principles calculations and thin-lm growth. Physical Review B, 96(19), [195417]. DOI: 10.1103/PhysRevB.96.195417 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. XU10127B PRB October 31, 2017 2:38 1 PHYSICAL REVIEW B 00, 005400 (2017) 2 Phonon thermal conductivity of scandium nitride for thermoelectrics from first-principles 3 calculations and thin-film growth 1,* 1,2 3 3 1 4 1 4 Sit Kerdsongpanya, Olle Hellman, Bo Sun, Yee Kan Koh, Jun Lu, Ngo Van Nong, Sergei I. Simak, 1,5 1,† 5 Björn Alling, and Per Eklund 1 6 Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden 2 7 Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA 3 8 Department of Mechanical Engineering, National University of Singapore, Block EA, 9 Engineering Drive 1, #07-08, 117576 Singapore 4 9 Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Frederiksborgvej 399, 10 Building 779, 4000 Roskilde, Denmark 5 11 Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany 13 (Received 2 July 2016; revised manuscript received 6 October 2017; published xxxxxx) 14 The knowledge of lattice thermal conductivity of materials under realistic conditions is vitally important since 15 many modern technologies require either high or low thermal conductivity. Here, we propose a theoretical model 16 for determining lattice thermal conductivity, which takes into account the effect of microstructure. It is based 17 on ab initio description that includes the temperature dependence of the interatomic force constants and treats 18 anharmonic lattice vibrations. We choose ScN as a model system, comparing the computational predictions to 19 the experimental data by time-domain thermoreflectance. Our experimental results show a trend of reduction 20 in lattice thermal conductivity with decreasing domain size predicted by the theoretical model. These results 21 suggest a possibility to control thermal conductivity by microstructural tailoring and provide a predictive tool for 22 the effect of the microstructure on the lattice thermal conductivity of materials based on ab initio calculations. 23 DOI: 10.1103/PhysRevB.00.005400 24 Design of modern materials inevitably requires taking the conductivity from first principles. In the present paper, 53 25 thermal conductivity into account [1]. For thermoelectric we combine state-of-the-art computational techniques with 54 26 materials a low thermal conductivity is crucial to avoid characterization and measurements to determine the effect of 55 27 heat transfer across the legs and therefore loss in energy microstructure on the thermal conductivity of ScN thin films. 56 28 conversion efficiency [2]. In contrast, electronic components When discussing thermal properties from a computational 57 29 require packaging materials with high thermal conductivity to perspective, the lattice dynamical Hamiltonian 58 30 efficiently dissipate the generated heat [3]. Furthermore, the 2 pi 1 αβ α β 31 more complex the devices become, the higher is the demand H = U + + u u 0 2m 2! ij i j 32 to control the interplay between microstructure and thermal i i ij αβ 33 performance [4,5]. For hard protective wear-resistant coatings, 1 αβγ α β γ 34 in, e.g., cutting or milling applications, thermal properties + u u u + ..., (1) 3! ij k i j k 35 are often barely considered when optimizing mechanical and ij kαβγ 36 tribological properties, despite the fact that the workpiece is ◦ is the starting point. It relates the energy of the lattice 59 37 typically subject to temperatures locally exceeding 1100 C to displacements (u) of atoms from equilibrium, with a 60 38 in the contact spots [6–8]. The requirements for thermal proportionality constant () for each pair, triplet, quartet, and 61 39 conductivity are therefore high: the in-plane heat spread within so on, where ijk are indices of atoms and αβγ are Cartesian 62 40 the coating should be as high as possible to ensure uniform indices. Traditionally, these interatomic force constants 63 41 heating, while the cross-plane thermal conductivity should are determined by the Taylor expansion of the zero-Kelvin 64 42 be as low as possible to minimize the heat load on the energy around the equilibrium positions, assuming that this 65 43 substrate [6–8].These examples underscore how important it expansion is also valid at high temperatures. In this paper we 66 44 is to understand and be able to tailor thermal conductivity in use a recently developed technique, the temperature-dependent 67 45 materials in a broad range of applications. effective potential (TDEP) [11–13], where ’s are extracted 68 46 Measurements of thermal conductivity are relatively stan- from the finite-temperature ab initio molecular dynamics. 69 47 dard for bulk materials but much more challenging for thin This provides their intrinsic temperature dependence and the 70 48 films and nanoscale materials, still being the topic of active ability to model phenomena inaccessible by traditional means 71 49 method development [9,10]. There is therefore a substantial [14,15]. 72 50 need to also develop theoretical methods for predicting or To address these general research questions, we choose 73 51 simulating the thermal conductivity of real materials. Recent scandium nitride as a model system. There is an increasing 74 52 advances in methodology allow us to predict the thermal interest in ScN for a wide range of applications [16], such 75 as a dislocation-reducing buffer for group III nitrides [17]or 76 as a potential thermoelectric material because of its relatively 77 * Present address: Department of Materials Science and Engineer- large Seebeck coefficient S accompanied by low-resistivity 78 2 ing, Rensselaer Polytechnic Institute, Troy, New York 12180, USA. ρ that results in a high thermoelectric power factor (S /ρ) 79 † −3 −1 −2 Corresponding author: [email protected] of about 2.5−3.3 × 10 Wm K [18–21]. ScN can also 80 2469-9950/2017/00(00)/005400(6) 005400-1 ©2017 American Physical Society ACC. CODE XU10127B AUTHOR Kerdsongpanya XU10127B PRB October 31, 2017 2:38 SIT KERDSONGPANYA et al. PHYSICAL REVIEW B 00, 005400 (2017) 81 be made p type by doping on Sc sites [22,23]. The former by x-ray diffraction (XRD) with standard θ-2θ scans using 140 82 application requires a high thermal conductivity, while the CuKα radiation in a Philips PW 1820 diffractometer. Cross- 141 83 latter requires it to be low. With an indirect gap of 0.9 eV, section transmission electron microscopy (TEM) and plan- 142 84 the thermal conductivity of ScN will be dominated by the view scanning electron microscopy (SEM) were performed on 143 85 lattice contribution [24–27]. In an ideal harmonic material, all samples to investigate film microstructure and morphology. 144 86 nothing prevents phonons from carrying heat. In practice, For cross-section TEM, the samples were prepared by gluing 145 87 scattering from impurities or isotopes, grain boundaries, and two pieces of the sample face to face into a Ti grid, 146 88 the intrinsic anharmonicity result in a finite phonon lifetime. then polishing down to 50-μm thickness. Ion milling was 147 89 Sc is isotopically pure. A large single crystal of pure ScN performed in a Gatan Precision Ion Polishing System at 148 + ◦ 90 would leave the intrinsic anharmonicity as the sole scattering Ar energy of 5 keV and a gun angle of 5 , with a final 149 + ◦ 91 mechanism. Any alloying dopant would decrease thermal polishing step with 2-keV Ar energy and angle of 2 . TEM 150 92 conductivity more than in a material with natural isotopic characterization was performed using a Tecnai G2 TF20UT 151 93 defects, as the majority of heat is carried by acoustic phonons, with a field-emission gun. A ULVAC-RIKO ZEM3 system 152 94 rendering the N isotopic distribution less important. This is was used to measure the Seebeck coefficient and electrical 153 95 therefore an opportunity for tailoring the thermal conductivity, resistivity of the films simultaneously in a low-pressure helium 154 96 by controlling the microstructure. atmosphere from room temperature. The error bar of these 155 97 The temperature-dependent phonon thermal conductivity of measurements is within 7%, and the substrate contribution to 156 98 ScN was obtained with ab initio Born-Oppenheimer molecular the Seebeck coefficient and electrical resistivity is negligible.
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