Thermal conductivity of mesoporous films measured by Raman spectroscopy

Stoib, Benedikt; Filser, S.; Petermann, Nils; Wiggers, Hartmut; Stutzmann, M.; Brandt, Martin S.

doi:10.1063/1.4873539

Cited by 20 publications

(21 citation statements)

References 34 publications

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“…In this section we will present applications of the Raman shift method to two Si-based samples, a bulk-like 3-dimensional material of dense nanocrystalline Si with considerable oxygen content and of a porous thin film of Si 78 Ge 22 . 10,45,[81][82][83][84][85] Both material systems are fabricated from the same type of raw material, which is a powder of gas phase synthesized nanocrystals of Si and SiGe, respectively. Among other possible applications, these materials are of considerable interest within the framework of thermoelectrics.…”

Section: Application Of the Raman Shift Methodsmentioning

confidence: 99%

Spatially resolved determination of thermal conductivity by Raman spectroscopy

Stoib¹,

Filser²,

Stötzel³

et al. 2014

Semicond. Sci. Technol.

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We review the Raman shift method as a non-destructive optical tool to investigate the thermal conductivity and demonstrate the possibility to map this quantity with a micrometer resolution by studying thin film and bulk materials for thermoelectric applications. In this method, a focused laser beam both thermally excites a sample and undergoes Raman scattering at the excitation spot. The temperature dependence of the phonon energies measured is used as a local thermometer. We discuss that the temperature measured is an effective one and describe how the thermal conductivity is deduced from single temperature measurements to full temperature maps, with the help of analytical or numerical treatments of heat diffusion. We validate the method and its analysis on 3-and 2-dimensional single crystalline samples before applying it to more complex Si-based materials. A suspended thin mesoporous film of phosphorus-doped laser-sintered Si 78 Ge 22 nanoparticles is investigated to extract the in-plane thermal conductivity from the effective temperatures, measured as a function of the distance to the heat sink. Using an iterative multigrid Gauss-Seidel algorithm the experimental data can be modelled yielding a thermal conductivity of 0.1 W/m K after normalizing by the porosity. As a second application we map the surface of a phosphorus-doped 3-dimensional bulknanocrystalline Si sample which exhibits anisotropic and oxygen-rich precipitates. Thermal conductivities as low as 11 W/m K are found in the regions of the precipitates, significantly lower than the 17 W/m K in the surrounding matrix. The present work serves as a basis to more routinely use the Raman shift method as a versatile tool for thermal conductivity investigations, both for samples with high and low thermal conductivity and in a variety of geometries.

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Section: Application Of the Raman Shift Methodsmentioning

confidence: 99%

Spatially resolved determination of thermal conductivity by Raman spectroscopy

Stoib¹,

Filser²,

Stötzel³

et al. 2014

Semicond. Sci. Technol.

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“…Since 1999 6 , micro-Raman scattering is known to be an efficient photo-thermal technique for contactless measurement of thermal conductivity of various nanoscale materials [7][8][9] . This measurement approach uses the same laser beam for local thermal heating of the studied sample as arXiv:1609.08133…”

Section: Arxiv:160908133mentioning

confidence: 99%

Anisotropic heat conduction in silicon nanowire network revealed by Raman scattering

Isaiev

Didukh

Nychyporuk

et al. 2017

Applied Physics Letters

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Anisotropic nanomaterials possess interesting thermal transport properties because they allow orientation of heat fluxes along preferential directions due to a high ratio (up to three orders of magnitude) between their in-plane and cross-plane thermal conductivities. Among different techniques allowing thermal conductivity evaluation, micro-Raman scattering is known to be one of the most efficient contactless measurement approaches. In this letter, an experimental approach based on Raman scattering measurements with variable laser spot sizes is reported. Correlation between experimental and calculated thermal resistances of one-dimensional nanocrystalline solids allows simultaneous estimation of their in-plane and cross-plane thermal conductivities. In particular, our measurement approach is illustrated to be applied for anisotropic thermal conductivity evaluation of silicon nanowire arrays.

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“…[1][2][3][4][5] In particular concerning the morphology, an enhanced surface-to-volume ratio (or interface-to-volume ratio) is sometimes beneficial, e.g., for improving chemical reactivity, charge separation, optical absorption or phonon scattering. [6][7][8][9][10][11][12] The fabrication of such structurally and electronically tailored materials can be complicated, expensive, or might require toxic substances, e.g., phosphine (PH 3 ) for doping in the gas phase. Various techniques are known to incorporate and activate dopants after the synthesis of the host material itself, e.g., implantation or in-diffusion from solid or gaseous sources.…”

Section: Doi: 101002/aelm201400029mentioning

confidence: 99%

Laser‐Assisted Wet‐Chemical Doping of Sintered Si and Ge Nanoparticle Films

Stoib

Greppmair

Petermann

et al. 2015

Adv Elect Materials

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Doped thin films of group‐IV semiconductors can be fabricated using the adsorption of dopant species from a liquid source to a precursor nanoparticle film, followed by laser‐sintering to incorporate and activate the dopants in the sintered thin film. A detailed study of the doping of germanium films with arsenic reveals diffusion of dopants into the film and their adsorption to the nanoparticle surface as kinetically governing steps, benefiting from the large internal surface area of the nanoparticle film. The resulting charge carrier concentration can be adjusted by the internal surface area via the nanoparticle diameter, by controlling the dopant concentration in the liquid, and by the immersion time and temperature. It is shown that the method can be successfully transferred to silicon and silicon–germanium alloy films using group‐III and ‐V elements, which lead to p‐ and n‐type conductivity, respectively. Atomic dopant concentrations above 1020 cm−3 can be realized by laser‐sintering, which are electrically active to a high extent and lead to effective conductivities well above 10 S cm–1 in the mesoporous films is investigated here. The method allows flexible printing of devices using inks for the nanoparticles and the dopant and avoids toxic substances for the doping of nanoparticles in the gas phase.

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Thermal conductivity of mesoporous films measured by Raman spectroscopy

Abstract: Monte Carlo simulation of cross-plane thermal conductivity of nanostructured porous silicon films

Cited by 20 publications

References 34 publications

Spatially resolved determination of thermal conductivity by Raman spectroscopy

Spatially resolved determination of thermal conductivity by Raman spectroscopy

Anisotropic heat conduction in silicon nanowire network revealed by Raman scattering

Laser‐Assisted Wet‐Chemical Doping of Sintered Si and Ge Nanoparticle Films

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