In-plane thermoelectric properties of Si/Ge superlattice

Liu, W.L.; Borca‐Tasciuc, Theodorian; Liu, J.L.; Taka, K.; Wang, K.L.; Dresselhaus, M. S.; Chen, G.

doi:10.1109/ict.2001.979901

Cited by 7 publications

(6 citation statements)

References 12 publications

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“…Consequently, these studies show that all three properties of the figure of merit are affected such that the zT is increased with a superlattice structure. In related and more recent work, Lee et al [9] showed the enhanced Seebeck coefficient for SrTiO 3 /SrTi 0.8 Nb 0.2 O 3 superlattices, and Liu et al [10] showed the promising in-plane thermoelectric (TE) properties on Si/Ge SLs. These more recent studies show increases of the figure of merit by an order of magnitude over bulk material.…”

Section: Introductionmentioning

confidence: 98%

Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering

Cramer

Farnell

et al. 2018

Coatings

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Multilayers (MLs) of 31 bi-layers and a 10-nm layer thickness each of Si/SiC were deposited on silicon, quartz and mullite substrates using a high-speed, ion-beam sputter deposition process. The samples deposited on the silicon substrates were used for imaging purposes and structural verification as they did not allow for accurate electrical measurement of the material. The Seebeck coefficient and the electrical resistivity on the mullite and the quartz substrates were reported as a function of temperature and used to compare the film performance. The thermal conductivity measurement was performed for ML samples grown on Si, and an average value of the thermal conductivity was used to find the figure of merit, zT, for all samples tested. X-ray diffraction (XRD) spectra showed an amorphous nature of the thin films. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the film morphology and verify the nature of the crystallinity. The mobility of the multilayer films was measured to be only 0.039 to 1.0 cm 2 /Vs at room temperature. The samples were tested three times in the temperature range of 300 K to 900 K to document the changes in the films with temperature cycling. The highest Seebeck coefficient is measured for a Si/SiC multilayer system on quartz and mullite substrates and were observed at 870 K to be roughly −2600 µV/K due to a strain-induced redistribution of the states' effect. The highest figure of merit, zT, calculated for the multilayers in this study was 0.08 at 870 K.

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Section: Introductionmentioning

confidence: 98%

Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering

Cramer

Farnell

et al. 2018

Coatings

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“…That is why, in recent years, a lot of work on superlattices has been carried out [3,4]. The advantages of thermal conductivity decrease [5,6] and power factor [7][8][9] increase are well known. Indeed, phonon diffusion on the Si-SiGe interfaces leads to a decrease of lattice thermal conductivity and a potential increase of the figure of merit ZT .…”

Section: Introductionmentioning

confidence: 99%

An innovating technological approach for Si–SiGe superlattice integration into thermoelectric modules

Savelli

Plissonnier

Remondière

et al. 2008

J. Micromech. Microeng.

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This paper presents the development of doped polycrystalline Si-SiGe superlattices as thermoelectric (TE) elements integrated into generators. The modules dimension is 1 cm 2 , Si and SiGe are in situ doped (n and p types) and realized by CVD (chemical vapor deposition) on a 4 inch (0 0 1) silicon wafer. Si-SiGe superlattice growth will be studied, as well as the integration into thermoelectric modules. Interest in using superlattices as TE materials will be justified by their thermal conductivity measurements. Moreover, process fabrication and different geometry designs will be presented. Finally, the first measurements realized on these modules allowed scavenging 320 mV for a temperature difference of 90 K.

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“…In addition, the RTA model requires the value of mobility in the direction of transport for electrical-conductivity calculations. Because of the conflict [8] and [30]- [33].…”

Section: Negf Formalismmentioning

confidence: 99%

“…In this case, the Seebeck coefficient showed only a very small change due to the constant well In addition to the effects of quantum confinement, the values used for the effective mass for silicon and germanium were found to have a significant effect on the predicted electricalconductivity values. For our calculations, we used the effective mass corresponding to bulk conductivity values, but the various experiments in [8], [30], [31], and [33] were performed on single crystalline epitaxial layers deposited on a graded Si x Ge 1−x substrate. For film thicknesses of the order of a few nanometers, as used in our calculations, both silicon and germanium can be considered to be single crystals, allowing us to use the effective mass for that particular orientation.…”

Section: Negf Formalismmentioning

confidence: 99%

Quantum Modeling of Thermoelectric Properties of Si/Ge/Si Superlattices

Bulusu

Walker

2008

IEEE Trans. Electron Devices

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Abstract-Using a nonequilibrium Green's function approach, quantum simulations are performed to assess the device characteristics for cross-plane transport in Si/Ge/Si-superlattice thin films. The effect of quantum confinement on the Seebeck coefficient and electrical transport and its impact on the power factor of superlattices are studied. In this case, decreasing well width leads to an increased subband spacing causing the Seebeck coefficient of the superlattice to decrease. Electron confinement also causes a drastic reduction in the overall available density of states. Results show that confinement effects in the silicon barrier are responsible for a 40% decrease in the electrical conductivity of superlattices where barrier films are thinner by a factor of 1.5. In the same two devices, there is a negligible change in the Seebeck coefficient, which results in a decrease in the power factor corresponding to the decrease in conductivity. This decrease in the electrical performance for superlattices with thinner layers may offset the previously hypothesized gains of highly scaled superlattice structures resulting from reduced thermal conductivity. Simulations of the present superlattice structure at varying doping levels show a decrease in power factor with a decrease in device size parameters.

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In-plane thermoelectric properties of Si/Ge superlattice

Cited by 7 publications

References 12 publications

Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering

Thermoelectric Properties and Morphology of Si/SiC Thin-Film Multilayers Grown by Ion Beam Sputtering

An innovating technological approach for Si–SiGe superlattice integration into thermoelectric modules

Quantum Modeling of Thermoelectric Properties of Si/Ge/Si Superlattices

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