Reduction of the thermal conductivity of the thermoelectric material ScN by Nb alloying

Tureson, Nina; Nong, Ngo Van; Fournier, Danièle; Singh, Niraj K.; Acharya, S.; Schmidt, Susann; Belliard, Laurent; Soni, Ajay; Febvrier, Arnaud Le; Eklund, Per

doi:10.1063/1.4993913

Cited by 32 publications

(27 citation statements)

References 37 publications

(24 reference statements)

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“…shows the thermal conductivity of the Mg-implanted ScN films. The value of the thermal conductivity of the ScN reference sample is similar to earlier reported values for ScN thin films (10-12 Wm -1 K -1 )[25,27,30,47]. The sample implanted at high temperature exhibits a thermal conductivity similar to the value of the reference sample ScN.With a temperature high enough to anneal out the defects, the difference is within the error bars and can thus be considered negligible in this case.…”

supporting

confidence: 87%

“…The lower (absolute) value of the Seebeck coefficient for ScN compared to earlier reported ScN films, is most likely due to the higher amount of oxygen contamination present in the film, especially the presence of oxide at grain boundaries and/or defects [18,19,32]. A presence of oxide at grain boundaries/defects affected the thermoelectric properties with a reduced Seebeck and electrical conductivity resulting to a low power factor [18,27].…”

Section: Methodsmentioning

confidence: 99%

“…ScN has favorable properties such as high carrier mobility (10-180 cm 2 V -1 s -1 ), carrier concentration in the range 10 18 -10 22 cm -3 [23], low electrical resistivity (~300 µΩ.cm) [19] and a narrow indirect band gap of around 0.9 eV [23,24]. In comparison with established thermoelectric materials like PbTe and Bi2Te3 [2], the power factor of ScN (2.5-3.3 Wm -1 K -2 ) [19,25] is in the same order of magnitude [19,[25][26][27][28][29]. However, the thermal conductivity is relatively high (10-12 W m -1 K -1 ) [25,30] and needs to be minimized for thermoelectric application.…”

Section: Introductionmentioning

confidence: 99%

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Effect of ion-implantation-induced defects and Mg dopants on the thermoelectric properties of ScN

et al. 2018

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For applications in energy harvesting, environmentally friendly cooling, and as power sources in remote or portable applications, it is desired to enhance the efficiency of thermoelectric materials. One strategy consists of reducing the thermal conductivity while increasing or retaining the thermoelectric power factor. An approach to achieve this is doping to enhance the Seebeck coefficient and electrical conductivity, while simultaneously introducing defects in the materials to increase phonon scattering. Here, we use Mg ion implantation to induce defects in epitaxial ScN (111) films. The films were implanted with Mg + ions with different concentration profiles along the thickness of the film, incorporating 0.35 to 2.2 at.% of Mg in ScN. Implantation at high temperature (600 ˚C), with few defects due to the temperature, does not substantially affect the thermal conductivity compared to a reference ScN. Samples implanted at room temperature, in contrast, exhibited a reduction of the thermal conductivity by a factor of three. The sample doped with 2.2 at.% Mg also showed an increased power factor after implantation. This study thus shows the effect of ion-induced defects on thermal conductivity of ScN films. High-temperature implantation allows the defects to be annealed out during implantation, while the defects are retained for room-temperature implanted samples, allowing for a drastic reduction in thermal conductivity.

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supporting

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of ion-implantation-induced defects and Mg dopants on the thermoelectric properties of ScN

et al. 2018

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“…The Seebeck coefficient of ScN is relatively large (reaching -180 lV=K at 800 K) and because of its low electrical resistivity, large power factors between 2.5 and 3.5 9 10 -3 Wm À1 K À2 have been reported [9,10]. Doping and alloying ScN with heavy elements [11,12] and/or creating artificial layer interfaces such as metal/semiconductor superlattices [13][14][15][16] can alter properties and decrease the thermal conductivity, resulting in an enhanced zT.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of phase stability, crystal and electronic structure of MeMgN2 (Me = Ti, Zr, Hf) compounds

et al. 2017

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Scandium nitride has recently gained interest as a prospective compound for thermoelectric applications due to its high Seebeck coefficient. However, ScN also has a relatively high thermal conductivity, which limits its thermoelectric efficiency and figure of merit (zT). These properties motivate a search for other semiconductor materials that share the electronic structure features of ScN, but which have a lower thermal conductivity. Thus, the focus of our study is to predict the existence and stability of such materials among inherently layered equivalent ternaries that incorporate heavier atoms for enhanced phonon scattering and to calculate their thermoelectric properties. Using density functional theory calculations, the phase stability of TiMgN 2 , ZrMgN 2 and HfMgN 2 compounds has been calculated. From the computationally predicted phase diagrams for these materials, we conclude that all three compounds are stable in these stoichiometries. The stable compounds may have one of two competing crystal structures: a monoclinic structure (LiUN 2 prototype) or a trigonal superstructure (NaCrS 2 prototype; R 3mH). The band structure for the two competing structures for each ternary is also calculated and predicts semiconducting behavior for all three compounds in the NaCrS 2 crystal structure with an indirect band gap and semiconducting behavior for ZrMgN 2 and HfMgN 2 in the monoclinic crystal structure with a direct band gap. Seebeck coefficient and power factors are also predicted, showing that all three compounds in both the NaCrS 2 and the LiUN 2 structures have large Seebeck coefficients. The predicted stability of these compounds suggests that they can be synthesized by, e.g., physical vapor deposition.

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“…The oxygen detected in those two films is mostly present as oxynitride. The film deposited on c-plane Al2O3 had a lower N/Sc ratio of 0.75 and contained a significant amount of oxygen,16 %, of which 10.3 % is due to ScOxN1-x (x > 0) and 5.6% due to an oxide. A lower TD yields ScN films containing higher content of oxygen (10-15 %), found as oxynitride and oxide and associated with lower ratio of N/Sc between 0.53 (c-plane Al2O3 substrate) and 0.79 (r-plane Al2O3 substrate).…”

mentioning

confidence: 99%

Effect of impurities on morphology, growth mode, and thermoelectric properties of (1 1 1) and (0 0 1) epitaxial-like ScN films

Febvrier

Tureson

Stilkerich

et al. 2018

J. Phys. D: Appl. Phys.

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ScN material is an emerging semiconductor with an indirect bandgap. It has attracted attention for its thermoelectric properties, use as seed layers, and for alloys for piezoelectric application. ScN or other transition metal nitride semiconductors used for their interesting electrical properties are sensitive to contaminants, such as oxygen or fluorine. In this present article, the influence of depositions conditions on the amount of oxygen contaminants incorporated in ScN films were investigated and their effects on the electrical properties (electrical resistivity and Seebeck coefficient) were studied. The epitaxial-like films of thickness 125  5 nm to 155 5 nm were deposited by D.C.-magnetron sputtering on c-plane Al2O3, MgO(111) and r-plane Al2O3 at a substrate temperature ranging from 700 C to 950 C. The amount of oxygen contaminants presents in the film, dissolved into ScN or as an oxide, was related to the adatom mobility during growth, which is affected by the deposition temperature and the presence of twin domain growth. The lowest values of electrical resistivity of 50  cm were obtained on ScN(111)/MgO (111) and on ScN(001)/r-plane Al2O3 grown at 950C with no twin domains and the lowest amount of oxygen contaminant. At the best, the films exhibited an electrical resistivity of 50  cm with Seebeck coefficient values maintained at -40 V K -1 , thus a power factor estimated at 3.2 10 -3 W m -1 K -2 (at room temperature).

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Reduction of the thermal conductivity of the thermoelectric material ScN by Nb alloying

Abstract: ScN-rich (Sc,Nb) . Insertion of Nb into ScN thus yielded to a reduction in thermal conductivity by a factor 5 due to the mass contrast in ScN which increase the phonon scattering ion the material.3

Cited by 32 publications

References 37 publications

Effect of ion-implantation-induced defects and Mg dopants on the thermoelectric properties of ScN

Effect of ion-implantation-induced defects and Mg dopants on the thermoelectric properties of ScN

Theoretical study of phase stability, crystal and electronic structure of MeMgN2 (Me = Ti, Zr, Hf) compounds

Effect of impurities on morphology, growth mode, and thermoelectric properties of (1 1 1) and (0 0 1) epitaxial-like ScN films

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