Enhanced thermoelectric properties in Bi/Te core/shell heterostructure nanowires through strain and interface engineering

Kim, Jeongmin; Kim, Gwansik; Bahk, Je‐Hyeong; Noh, Jin−Seo; Lee, Wooyoung

doi:10.1016/j.nanoen.2017.01.017

Cited by 15 publications

(21 citation statements)

References 36 publications

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“…One recent work was the characterization of GaAs/InAs nanowires by thermovoltage measurements in those situations when electrical conductance does not provide information [30]. Another study demonstrated enhanced thermoelectric properties in Bi/Te CSNs via strain effects [31].…”

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confidence: 99%

Reversal of Thermoelectric Current in Tubular Nanowires

et al. 2017

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We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign, i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector. The sign reversal can survive in the presence of impurities. We predict this result for core/shell nanowires, for uniform nanowires with surface states due to the Fermi level pinning, and for topological insulator nanowires. PACS numbers: 73.23.b, 73.50.Lw, 73.63.Nm, 73.50.Fqi A temperature gradient across a conducing material induces an energy gradient, which in turn results in particle transport. In an open circuit, where no net current flows, a voltage is then generated when two ends of a sample are maintained at different temperatures -this is the Seebeck effect and the linear voltage response is known as thermopower. The hotter particles have larger average kinetic energy, and the net particle flow is therefore generally from the hot to the cold side. The thermopower and thermoelectric current can be positive or negative, depending on the type of charge carriers, i.e., electrons or holes.In comparison to this macroscopic case, the thermopower at the nanoscale has special characteristics. For example, if the energy separation between the quantum states of the system is larger than the thermal energy the thermopower may alternate between positive and negative values, depending on the position of the Fermi level relatively to a resonant energy, which can be controlled with a gate voltage. These oscillations were predicted a long time ago [1], and subsequently experimentally observed in quantum dots [2][3][4], and in molecules [5]. A sign change in the thermopower can also be obtained by increasing the temperature gradient and thus the population of the resonant level [6][7][8][9]. In these examples the charge carriers are electrons and the sign change of the thermopower means that they travel from the cold side to the hot side, which may appear counterintuitive. Other nonlinear effects can occur if the characteristic relaxation length of electrons and or phonons exceeds the sample size [10], because the energy of electrons and/or phonons is no longer controlled by the temperature of the bath, but by the generated electric bias, including Coulomb interactions [11,12].Observing such negative thermopower at the nanoscale is difficult for at least two reasons: the currents tend to be small and it is hard to maintain a constant temperature difference across such short distances. Here we argue that a generic class of tubular nanowires, to be defined in more detail below, are ideal systems for both realizing and observing negative thermopower. Semiconductor nanowires are versatile syst...

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confidence: 99%

Reversal of Thermoelectric Current in Tubular Nanowires

et al. 2017

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“…The single crystalline Bi core was prepared by means of the on-lm formation of nanowires (OFFON) method as reported in ref. [9][10][11][12]. Bi thin lms were deposited by radio frequency sputtering on SiO 2 /Si substrates.…”

Section: Methodsmentioning

confidence: 99%

“…The reduction of l of Bi/TiO 2 2 (470 nm) can be attributed to an increase of charge carrier and phonon interface scattering comparable to the effect of the Te shell on the thermal conductivity of Bi/Te core/shell nanowires. [9][10][11] The compressive strain effect of the shell, which leads to a reduction of the electrical conductivity, will also lead to a reduction of the charge carrier contribution to the total thermal conductivity.…”

Section: Thermal Characterizationmentioning

confidence: 99%

“…For this reason, Bi-based core/shell nanowires have raised attention in recent years because of their increased thermoelectric performance for relatively large diameters (d > 300 nm). [9][10][11] Tellurium (Te) coated as shell on the Bi nanowire core can cause a semimetal to semiconductor transition due to the lattice mismatch of the Bi core and the Te shell. 10,11 An increased Seebeck coefficient and a reduced thermal conductivity can be the result of such a heterostructure.…”

Section: Introductionmentioning

confidence: 99%

“…[9][10][11] Tellurium (Te) coated as shell on the Bi nanowire core can cause a semimetal to semiconductor transition due to the lattice mismatch of the Bi core and the Te shell. 10,11 An increased Seebeck coefficient and a reduced thermal conductivity can be the result of such a heterostructure. However, the combined full thermoelectric characterization of individual Bibased core/shell nanowires, in which all transport parameters (s, S and l) are determined on one and the same nanowire, remains an open issue.…”

Section: Introductionmentioning

confidence: 99%

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Semimetal to semiconductor transition in Bi/TiO₂ core/shell nanowires

et al. 2021

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Anisotropic Electrical Conductivity and Isotropic Seebeck Coefficient Feature Induced High Thermoelectric Power Factor >1800 µW m⁻¹ K⁻² in MWCNT Films

Sun

Wang

et al. 2022

Adv Funct Materials

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Lightweight and low-cost flexible thermoelectric (TE) materials improve the heat-to-electricity conversion efficiency compared to rigid materials by minimizing the heat loss between TE devices and heat sources in waste heat recovery. Multi-walled carbon nanotube (MWCNT) has excellent mechanical and electrical properties. However, the TE power factor (PF) of MWCNTs is much lower than single/double-walled carbon nanotube (S/DWCNT), which is often lower than 40 µW m −1 -K −2 . Herein an effective way to achieve high PFs of ≈1800 µW m −1 -K −2 for p-type and ≈1000 µW m −1 -K −2 for n-type in flexible MWCNT films is reported. The high power factor is achieved by taking advantage of the anisotropic electrical conductivity and isotropic Seebeck coefficient feature of 1D CNTs as well as the following doping and cold-pressing to improve the electrical conductivity of MWCNT films. The PF values are comparable to that of state-of-the-art S/DWCNT films and most inorganic TE materials. A Lego-like TE generator (TEG) with an assembling structure is fabricated to show the heat-to-electricity ability of the materials, which exhibits the highest areal output power of ≈27 W m −2 among CNT-based flexible TEGs. This method may be extended to other 1D-material based composites to boost the development of high PF flexible TE materials.

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Enhanced thermoelectric properties in Bi/Te core/shell heterostructure nanowires through strain and interface engineering

Cited by 15 publications

References 36 publications

Reversal of Thermoelectric Current in Tubular Nanowires

Reversal of Thermoelectric Current in Tubular Nanowires

Semimetal to semiconductor transition in Bi/TiO₂ core/shell nanowires

Anisotropic Electrical Conductivity and Isotropic Seebeck Coefficient Feature Induced High Thermoelectric Power Factor >1800 µW m⁻¹ K⁻² in MWCNT Films

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Enhanced thermoelectric properties in Bi/Te core/shell heterostructure nanowires through strain and interface engineering

Cited by 15 publications

References 36 publications

Reversal of Thermoelectric Current in Tubular Nanowires

Reversal of Thermoelectric Current in Tubular Nanowires

Semimetal to semiconductor transition in Bi/TiO2 core/shell nanowires

Anisotropic Electrical Conductivity and Isotropic Seebeck Coefficient Feature Induced High Thermoelectric Power Factor >1800 µW m−1 K−2 in MWCNT Films

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Semimetal to semiconductor transition in Bi/TiO₂ core/shell nanowires

Anisotropic Electrical Conductivity and Isotropic Seebeck Coefficient Feature Induced High Thermoelectric Power Factor >1800 µW m⁻¹ K⁻² in MWCNT Films