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Stefan Dilhaire - One of the best experts on this subject based on the ideXlab platform.
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si and sige nanowires fabrication process and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Physical Chemistry C, 2013Co-Authors: Stephane Grauby, Etienne Puyoo, Jean-michel Rampnoux, Emmanuelle Rouviere, Stefan DilhaireAbstract:We have grown various samples of Si and SiGe nanowires (NWs), either by a classical vapor–liquid–solid (VLS) process or by chemical etching, to measure their thermal Conductivity and thus evaluate their efficiency for thermoelectrics applications. To do so, we have chosen a 3ω-Scanning Thermal Microscopy (SThM) imaging technique which is until now the only method able to perform topographical and thermal Measurements simultaneously on an assembly of individual NWs, leading to a statistical value of their thermal Conductivity. A size effect is clearly observed on Si NWs: 50 nm diameter NWs offer a reduced thermal Conductivity in comparison with 200 nm diameter or even larger NWs. On the contrary, the thermal Conductivity of SiGe NWs is widely reduced in comparison with the SiGe bulk value, even for large diameters, bigger than Si NWs ones. We discuss our results, comparing them with thermal Conductivity values from the literature obtained by other Measurement methods or models.
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Fabrication of Bi2Te3 nanowire arrays and thermal Conductivity Measurement by 3ω-scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: M. Muñoz Rojo, Jean-michel Rampnoux, Stephane Grauby, O. Caballero-calero, M. Martin-gonzalez, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 +/- 0.20) W/mK and (λNW) = (1.37 +/- 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtaining the thermal Conductivity of the whole as an effective medium. However, the 3ω-SThM presented here is the only technique able to measure the thermal Conductivity of single NWs embedded in a matrix as well as the thermal Conductivity of the composite locally. This technique is more versatile and straightforward than other methods to obtain the thermal Conductivity of nanostructures.
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fabrication of bi2te3 nanowire arrays and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: Miguel Munoz Rojo, Jean-michel Rampnoux, Olga Caballerocalero, Marisol Martingonzalez, Stephane Grauby, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 ± 0.20) W/mK and (λNW) = (1.37 ± 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtai...
Yi He - One of the best experts on this subject based on the ideXlab platform.
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rapid thermal Conductivity Measurement with a hot disk sensor part 1 theoretical considerations
Thermochimica Acta, 2005Co-Authors: Yi HeAbstract:Abstract The hot disk technique represents a transient plane source method for rapid thermal Conductivity and thermal diffusivity Measurement. The main advantages of the hot disk technique include: wide thermal Conductivity range, from 0.005 W/(m K) to 500 W/(m K); wide range of materials types, from liquid, gel to solid; easy sample preparation; non-destructive; and more importantly, high accuracy. In this paper, the basic theory of thermal Conductivity Measurement with hot disk sensor will be discussed. Starting from the instantaneous point source solution, the mathematical expression of the average temperature change in the sensor surface during a hot disk Measurement will be derived. This temperature change, which can be accurately determined by measuring the electrical resistance of the sensor, is highly dependent on the thermal transport properties of the surrounding material. By analyzing this temperature change as a function of time, it is possible to deduce the thermal Conductivity and the thermal diffusivity of the surrounding material. Several practical considerations, from sample size requirement to the elimination of thermal contact resistance, will also be discussed.
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rapid thermal Conductivity Measurement with a hot disk sensor part 2 characterization of thermal greases
Thermochimica Acta, 2005Co-Authors: Yi HeAbstract:Thermal transport properties of several thermal greases with applications in electronic packaging have been characterized at room temperature using the hot disk technique, which is a transient plane source technique for rapid thermal Conductivity and thermal diffusivity Measurement. In this technique, the hot disk sensor serves as a heat source and a thermometer. During the Measurement, the sensor is sandwiched between two halves of a sample, and a constant current is supplied to the sensor. The temperature increase at the sensor surface is strongly dependent on the thermal transport properties of the surrounding material. By monitoring the temperature increase as a function of time, one can determine the thermal Conductivity and the thermal diffusivity of the surrounding material with high accuracy. The results on thermal greases are in good agreement with supplier data, which were obtained by another method.
Stephane Grauby - One of the best experts on this subject based on the ideXlab platform.
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si and sige nanowires fabrication process and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Physical Chemistry C, 2013Co-Authors: Stephane Grauby, Etienne Puyoo, Jean-michel Rampnoux, Emmanuelle Rouviere, Stefan DilhaireAbstract:We have grown various samples of Si and SiGe nanowires (NWs), either by a classical vapor–liquid–solid (VLS) process or by chemical etching, to measure their thermal Conductivity and thus evaluate their efficiency for thermoelectrics applications. To do so, we have chosen a 3ω-Scanning Thermal Microscopy (SThM) imaging technique which is until now the only method able to perform topographical and thermal Measurements simultaneously on an assembly of individual NWs, leading to a statistical value of their thermal Conductivity. A size effect is clearly observed on Si NWs: 50 nm diameter NWs offer a reduced thermal Conductivity in comparison with 200 nm diameter or even larger NWs. On the contrary, the thermal Conductivity of SiGe NWs is widely reduced in comparison with the SiGe bulk value, even for large diameters, bigger than Si NWs ones. We discuss our results, comparing them with thermal Conductivity values from the literature obtained by other Measurement methods or models.
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Fabrication of Bi2Te3 nanowire arrays and thermal Conductivity Measurement by 3ω-scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: M. Muñoz Rojo, Jean-michel Rampnoux, Stephane Grauby, O. Caballero-calero, M. Martin-gonzalez, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 +/- 0.20) W/mK and (λNW) = (1.37 +/- 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtaining the thermal Conductivity of the whole as an effective medium. However, the 3ω-SThM presented here is the only technique able to measure the thermal Conductivity of single NWs embedded in a matrix as well as the thermal Conductivity of the composite locally. This technique is more versatile and straightforward than other methods to obtain the thermal Conductivity of nanostructures.
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fabrication of bi2te3 nanowire arrays and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: Miguel Munoz Rojo, Jean-michel Rampnoux, Olga Caballerocalero, Marisol Martingonzalez, Stephane Grauby, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 ± 0.20) W/mK and (λNW) = (1.37 ± 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtai...
Jean-michel Rampnoux - One of the best experts on this subject based on the ideXlab platform.
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si and sige nanowires fabrication process and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Physical Chemistry C, 2013Co-Authors: Stephane Grauby, Etienne Puyoo, Jean-michel Rampnoux, Emmanuelle Rouviere, Stefan DilhaireAbstract:We have grown various samples of Si and SiGe nanowires (NWs), either by a classical vapor–liquid–solid (VLS) process or by chemical etching, to measure their thermal Conductivity and thus evaluate their efficiency for thermoelectrics applications. To do so, we have chosen a 3ω-Scanning Thermal Microscopy (SThM) imaging technique which is until now the only method able to perform topographical and thermal Measurements simultaneously on an assembly of individual NWs, leading to a statistical value of their thermal Conductivity. A size effect is clearly observed on Si NWs: 50 nm diameter NWs offer a reduced thermal Conductivity in comparison with 200 nm diameter or even larger NWs. On the contrary, the thermal Conductivity of SiGe NWs is widely reduced in comparison with the SiGe bulk value, even for large diameters, bigger than Si NWs ones. We discuss our results, comparing them with thermal Conductivity values from the literature obtained by other Measurement methods or models.
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Fabrication of Bi2Te3 nanowire arrays and thermal Conductivity Measurement by 3ω-scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: M. Muñoz Rojo, Jean-michel Rampnoux, Stephane Grauby, O. Caballero-calero, M. Martin-gonzalez, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 +/- 0.20) W/mK and (λNW) = (1.37 +/- 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtaining the thermal Conductivity of the whole as an effective medium. However, the 3ω-SThM presented here is the only technique able to measure the thermal Conductivity of single NWs embedded in a matrix as well as the thermal Conductivity of the composite locally. This technique is more versatile and straightforward than other methods to obtain the thermal Conductivity of nanostructures.
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fabrication of bi2te3 nanowire arrays and thermal Conductivity Measurement by 3ω scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: Miguel Munoz Rojo, Jean-michel Rampnoux, Olga Caballerocalero, Marisol Martingonzalez, Stephane Grauby, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 ± 0.20) W/mK and (λNW) = (1.37 ± 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtai...
M. Muñoz Rojo - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of Bi2Te3 nanowire arrays and thermal Conductivity Measurement by 3ω-scanning thermal microscopy
Journal of Applied Physics, 2013Co-Authors: M. Muñoz Rojo, Jean-michel Rampnoux, Stephane Grauby, O. Caballero-calero, M. Martin-gonzalez, Stefan DilhaireAbstract:Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal Conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal Conductivity as well as the thermal Conductivity of the NWs to be, respectively, (λC) = (1.68 +/- 0.20) W/mK and (λNW) = (1.37 +/- 0.20) W/mK, showing a slight thermal Conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal Conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtaining the thermal Conductivity of the whole as an effective medium. However, the 3ω-SThM presented here is the only technique able to measure the thermal Conductivity of single NWs embedded in a matrix as well as the thermal Conductivity of the composite locally. This technique is more versatile and straightforward than other methods to obtain the thermal Conductivity of nanostructures.