Enhancement of the Thermoelectric Performance of Si-Ge Nanocomposites Containing a Small Amount of Au and Optimization of Boron Doping

Omprakash, Muthusamy; Ghodke, Swapnil; Singh, Saurabh; Delime-Codrin, Kévin; Nishino, Shunsuke; Adachi, Masahiro; Yamamoto, Yoshiyuki; Matsunami, Masaharu; Harish, S.; Shimomura, Masaru; Takeuchi, Tsunehiro

doi:10.1007/s11664-019-07857-5

Cited by 11 publications

(14 citation statements)

References 20 publications

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“…A comparison of the power factor of the obtained ptype Ca-Mg-Si film with those of the other p-type silicides reveals that the power factor of the present Ca-Mg-Si film is smaller than those reported for Sr-Si and Si-Ge films. [25][26][27] On the other hand, the present n-type films show better properties compared with the other silicides, but is smaller than widely investigated materials such as Bi-Te and Ag-Se. 28,29 However, it is possible to improve the present power factor by using doping to optimize the carrier concentration.…”

Section: Electrical Propertiesmentioning

confidence: 73%

Composition Dependence of Crystal Structures and Electrical Properties of Ca-Mg-Si Films Prepared by Sputtering

Katagiri

Uehara

Kurokawa

et al. 2020

Journal of Elec Materi

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Ca-Mg-Si ternary films were deposited at 300-335°C on (001)Al 2 O 3 substrates by a radio-frequency magnetron sputtering. Amorphous films were obtained for a wide range of compositions but not for single-phase CaMgSi. For all compositions, the electrical conductivity of the as-deposited films increased with the increase in temperature up to 400°C. The conduction type was controlled mainly by changing the Si/(Ca + Mg + Si) ratios of the films, and films with p-and n-type conductions were observed respectively with Si/(Ca + Mg + Si) ratios below 0.6 and above 0.7 along a fixed Ca/(Ca + Mg) ratio of about 0.50. A high thermoelectric power factor above 140 lW/(m K 2 ) with ptype conduction was obtained at 400°C for an amorphous-phase film.

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Section: Electrical Propertiesmentioning

confidence: 73%

Composition Dependence of Crystal Structures and Electrical Properties of Ca-Mg-Si Films Prepared by Sputtering

Katagiri

Uehara

Kurokawa

et al. 2020

Journal of Elec Materi

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“…The substitution of Ni for Si/Ge was employed to modify the electronic structure for enhancing the Seebeck coefficient. The boron doping was also employed to increase the hole concentration for optimizing the Fermi level position. − …”

Section: Resultsmentioning

confidence: 99%

“…Recently, we succeeded in developing a p -type Si–Ge alloy structure showing high ZT s of 1.38 and 1.63 at 973 K for thin film and bulk nanostructured composites, respectively. − In particular, an n -type Si–Ge alloy showed the highest ZT value ever reported, i.e., ∼1.88 at 873 K . This improvement was attributed to the synergetic enhancement of PF and reduced thermal conductivity, which was caused by (a) creation of a sharp peak near the valence band via Au-5d element substitution ( p -type Si–Ge, ZT = 1.38 and 1.63) and conduction band via Fe-3d element substitution ( n -type Si–Ge, ZT = 1.88), (b) optimized carrier concentration by boron doping for the p -type Si–Ge and phosphorus doping for the n -type Si–Ge, and (c) phonons scattered at the nanostructured grain interfaces.…”

Section: Introductionmentioning

confidence: 99%

“…An ultrasonic pulse receiver (Olympus 5072PR) was used to determine the sound velocity of samples at room temperature. The details about the sound velocity measurement are reported elsewhere. , The Hall coefficient was determined using a Quantum Design-made Physical Properties Measurement System (PPMS). The carrier concentrations ( n H ) were calculated from the Hall coefficient ( R H ), where n H = − R H –1 |e| –1 and e is the unit charge of the electron.…”

Section: Introductionmentioning

confidence: 99%

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Synergetic Enhancement of the Power Factor and Suppression of Lattice Thermal Conductivity via Electronic Structure Modification and Nanostructuring on a Ni- and B-Codoped p-Type Si–Ge Alloy for Thermoelectric Application

Omprakash

Singh

Hirata

et al. 2021

ACS Appl. Electron. Mater.

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In this study, the strategies of modifying the electronic structure, tuning carrier concentration, and nanostructuring were implemented to improve the power factor and reduce the thermal conductivity of Si−Ge simultaneously. The Si 0.65−x Ge 0.32 Ni 0.03 B x (x = 0.01, 0.02, 0.03, and 0.04) nanostructure was synthesized by high-energy ball-milling. Subsequently, a highpressure with low-temperature sintering process was carried out. A small amount of nickel (Ni) and boron (B) was introduced into Si−Ge to modify the electronic structure and optimize the carrier concentration. The sintered sample Si 0.62 Ge 0.32 Ni 0.03 B 0.03 showed a high power factor of 2.3 mW m −1 K −2 at 1000 K, which was influenced by the modified electronic structure and optimized carrier concentration. In addition, the thermal conductivity was effectively decreased to 1.47 W m −1 K −1 due to the phonon scattering by the micro to nanoscale grain boundaries. Ultimately, a large dimensionless figure of merit ZT ∼1.56 was obtained at 1000 K. Therefore, following these strategies can improve the thermoelectric performance of earth-abundant, environmentally friendly, and nontoxic Si−Ge material.

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“…The Joule heating from the leakage current and the absorbed laser power certainly led to a slight increase in the temperature of the device (see supplemental material for the detail of calculation [28][29][30][31][32][33][34][35][36] ). However, the temperature dependence of the thermal diffusivity, specific heat, and density of amorphous Si-Ge-Au alloy and SiO 2 are very weak at 300-500 K, 29,32,34,36) and the thermal conductivity of Si decrease with increasing temperature above room temperature. The minor effects related to these temperature increases and temperature dependences should not explain the bias-voltage-dependent behavior of Fig.…”

Section: Resultsmentioning

confidence: 99%

Capacitor-type thin-film heat flow switching device

Hirata¹,

Matsunaga²,

Singh³

et al. 2021

Jpn. J. Appl. Phys.

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We developed a capacitor-type heat flow switching device, in which electron thermal conductivity of the electrodes is actively controlled through the carrier concentration varied by an applied bias voltage. The device consisted of an amorphous p-type Si–Ge–Au alloy layer, an amorphous SiO2 as the dielectric layer, and an n-type Si substrate. Both amorphous materials are characterized by very low lattice thermal conductivity, ≤1 W m–1 K–1. The Si–Ge–Au amorphous layer with 40 nm in thickness was deposited by means of molecular beam deposition technique on the 100 nm thick SiO2 layer formed at the top surface of Si substrate. Bias voltage-dependent heat flow density through the fabricated device was evaluated by a time-domain thermoreflectance method at room temperature. Consequently, we observed a 55% increase in the heat flow density at the maximum.

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Enhancement of the Thermoelectric Performance of Si-Ge Nanocomposites Containing a Small Amount of Au and Optimization of Boron Doping

Cited by 11 publications

References 20 publications

Composition Dependence of Crystal Structures and Electrical Properties of Ca-Mg-Si Films Prepared by Sputtering

Composition Dependence of Crystal Structures and Electrical Properties of Ca-Mg-Si Films Prepared by Sputtering

Synergetic Enhancement of the Power Factor and Suppression of Lattice Thermal Conductivity via Electronic Structure Modification and Nanostructuring on a Ni- and B-Codoped p-Type Si–Ge Alloy for Thermoelectric Application

Capacitor-type thin-film heat flow switching device

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