Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

Mušić, Denis; Hunold, O.; Coultas, Sarah; Roberts, Adam

doi:10.1016/j.ssc.2017.04.016

Cited by 4 publications

(4 citation statements)

References 66 publications

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“…With the thermal conductivity data from this work (NbO/Ni 0.75 Ta 0.25 O) and the previously published Seebeck coefficient and electrical resistivity values for Nb 1.23 O/Ni 0.77 Ta 0.23 O x-ray amorphous multilayers [17], it is possible to estimate the thermoelectric figure of merit. Even though the figure of merit increases with an increasing temperature, it is within 0.1 below 650 K. This is a very small value compared to that of commercial thermoelectrics [21], but it may be enhanced at higher temperatures and by systematic compositional and multilayer period modulations, which is beyond the scope of current study.…”

Section: Resultsmentioning

confidence: 78%

“…With additions of N, filling the non-metallic vacant sites, the Seebeck coefficient and electrical resistivity of −70 µV K −1 and 500 µΩ m can be obtained at a temperature of 800 K, respectively [16]. In an amorphous and nanolaminated state (multilayered with Ni-Ta-O) it exhibits a low metallic resistivity in the range of 20 µΩ m at temperatures below 900 K, while maintaining the Seebeck coefficient of −25 µV K −1 [17]. Besides the possibility for energy generation uses, NbO is also very promising for memory applications [18], such as memristor networks in neuromorphic computing [19], and other electronic devices [20].…”

Section: Introductionmentioning

confidence: 99%

“…In this work, the thermal conductivity of amorphous NbO is studied using experimental and theoretical means. The working hypothesis is that NbO exhibits a high thermal conductivity value due to its low electrical resistivity (high electrical conductivity) [17], as suggested by the Wiedemann-Franz law [27]. This in turn implies that only electrons contribute to the thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

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On thermal conductivity of amorphous niobium monoxide

Mušić¹,

Prünte²,

Keuter³

et al. 2020

J. Phys. D: Appl. Phys.

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Thermal conductivity of NbO is studied experimentally and theoretically. Sputtered NbO samples, slightly overstoichiometric in oxygen, are x-ray amorphous with a combined NbO and NbO 2 short-range order, which is consistent with the quantum mechanical data. Upon annealing, NbO 2 crystallites form in the amorphous matrix due to an energetic preference of 44 meV atom −1 over NbO counterparts. The measured thermal conductivity at room temperature using time-domain thermoreflectance is 6.9 W m −1 K −1 , followed by a continuous increase due to electronic contributions, and it yields a total increase of 40 W m −1 K −1 at 650 K partly due to crystallisation. Phonon-phonon scattering can be induced by introducing Ni 0.75 Ta 0.25 O layers in NbO. These multilayers exhibit a thermal conductivity of 5.4 W m −1 K −1 at room temperature and a monotonic drop upon increasing temperature. It is thus feasible to modulate the high-temperature thermal conductivity of amorphous NbO by an order of magnitude. Hence, amorphous NbO may be of interest for thermoelectric devices, sensors and thermal insulation applications.

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Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On thermal conductivity of amorphous niobium monoxide

Mušić¹,

Prünte²,

Keuter³

et al. 2020

J. Phys. D: Appl. Phys.

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“…A low‐dimensional structure has a different density of states (DOS) distribution compared to a 3D system because of the quantum confinement effect, which can increase S without a substantial decrease of σ (Scheme 1b). [ 30–34 ] Despite the advantages of 2D RP structures, 2D Sn‐based OHPs have not yet been considered for TE applications.…”

Section: Introductionmentioning

confidence: 99%

Enhancing Thermoelectric Power Factor of 2D Organometal Halide Perovskites by Suppressing 2D/3D Phase Separation

et al. 2021

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Organometal halide perovskites (OHPs) exhibit superior charge transport characteristics and ultralow thermal conductivities. However, thermoelectric (TE) applications of OHPs have been limited because of difficulties in controlling their carrier concentration, which is a key to optimizing their TE properties. Here, facile control of the carrier concentration in Sn‐based OHPs is achieved by developing 2D crystal structures. The 2D OHP crystals are laterally oriented using a mixed solvent, and the morphology and crystal structure of the coexisting 2D/3D hybrid structures are systematically controlled via doping with methylammonium chloride. The effective number neff of inorganic octahedron layers in the 2D OHPs shows a strong positive correlation with the carrier concentration. Moreover, the 2D structure induces the quantum confinement effect, which enhances both the Seebeck coefficient and the electrical conductivity. A 2D OHP shows a high power factor of 111 µW m−1 K−2, which is an order of magnitude greater than the power factor of its 3D counterpart.

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Physical origin of inertness of Ta contacts on Bi2Te3

Mušić

Chen

Holzapfel

et al. 2018

Journal of Applied Physics

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Interfacial reactions and underlying atomic mechanisms between Ta contacts (space group Im3¯m) and thermoelectric Bi2Te3 (space group R3¯m) are studied experimentally and theoretically. A Ta/Bi2Te3 mixture is found to be inert up to the melting point of Bi2Te3 (∼589 °C) based on calorimetry and interfacial composition analyses. This can be understood using density functional theory. Bi and Te adatoms hop across a close-packed Ta(110) surface in the <111>, <110>, and <100> directions with the highest dwelling time on equilibrium (fourfold hollow) sites, but they do not exchange with Ta surface atoms. To identify the electronic structure fingerprint of Ta(110) inertness, the adsorption energies and electron density distributions are calculated for the Bi2Te3 constituting atoms and possible dopants (15 elements) stemming from C, N, and O groups. C, N, O, and S strongly adsorb to Ta(110), exhibiting enhanced reactivity. We propose that these four species can initiate exchange diffusion with Ta due to ionic interactions between Ta and the adsorbates. Our results imply that elements with a high electronegativity should be avoided in Bi2Te3 doping because interfacial interactions may occur, degrading its stability and transport properties.

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Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

Cited by 4 publications

References 66 publications

On thermal conductivity of amorphous niobium monoxide

On thermal conductivity of amorphous niobium monoxide

Enhancing Thermoelectric Power Factor of 2D Organometal Halide Perovskites by Suppressing 2D/3D Phase Separation

Physical origin of inertness of Ta contacts on Bi2Te3

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