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Effect of grain size on thermal transport in post-annealed antimony telluride thin films.

Park NW, Lee WY, Hong JE, Park TH, Yoon SG, Im H, Kim HS, Lee SK - Nanoscale Res Lett (2015)

Bottom Line: The measured total thermal conductivities of 400-nm-thick thin films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C were determined to be 2.0 to 3.7 W/m · K in the 20 to 300 K temperature range.We found that the film grain size, rather than the strain, had the most prominent effect on the reduction of the total thermal conductivity.To confirm the effect of grain size on temperature-dependent thermal transport in the thin films, the experimental results were analyzed using a modified Callaway model approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea.

ABSTRACT
The effects of grain size and strain on the temperature-dependent thermal transport of antimony telluride (Sb2Te3) thin films, controlled using post-annealing temperatures of 200°C to 350°C, were investigated using the 3-omega method. The measured total thermal conductivities of 400-nm-thick thin films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C were determined to be 2.0 to 3.7 W/m · K in the 20 to 300 K temperature range. We found that the film grain size, rather than the strain, had the most prominent effect on the reduction of the total thermal conductivity. To confirm the effect of grain size on temperature-dependent thermal transport in the thin films, the experimental results were analyzed using a modified Callaway model approach.

No MeSH data available.


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Measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3thin films. (a) Measured total thermal conductivity, κf = κL + κe, of 400-nm-thick Sb2Te3 films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C as a function of temperature. (b) Measured total thermal conductivity of film annealed at 300°C as a function of temperature (red in scatter plot). For comparison, the theoretically calculated total thermal conductivity (κf, solid line in red) with the two components of the thermal conductivity (the electronic (κe, dotted line in black) and lattice thermal conductivities (κL, solid line in blue)), are also included. κe was calculated from the out-of-plane electrical conductivity using the Wiedemann-Franz law.
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Fig5: Measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3thin films. (a) Measured total thermal conductivity, κf = κL + κe, of 400-nm-thick Sb2Te3 films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C as a function of temperature. (b) Measured total thermal conductivity of film annealed at 300°C as a function of temperature (red in scatter plot). For comparison, the theoretically calculated total thermal conductivity (κf, solid line in red) with the two components of the thermal conductivity (the electronic (κe, dotted line in black) and lattice thermal conductivities (κL, solid line in blue)), are also included. κe was calculated from the out-of-plane electrical conductivity using the Wiedemann-Franz law.

Mentions: Figure 5a shows the measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3 thin films as a function of temperature, from 20 to 300 K. As shown in Figure 5a, we found that the thermal conductivity of the films exhibits a strong dependence on the annealing temperature and grain-size in the 20 to 300 K temperature ranges. The observed reduction in the temperature-dependent total thermal conductivity was due to enhanced phonon boundary scattering following the decrease in grain size, as has been reported previously [16,35]. From Figure 5a, it can be seen that the total thermal conductivity decreases constantly after the approximately 50 K peak (the so-called ‘Umklapp peak’) has been reached, since the thin films at these temperatures are more significantly affected by phonon-phonon Umklapp scattering. For further understanding of lattice and electronic contribution in total thermal conductivity, we investigated a phonon transport model, which is based on the relaxation time and was previously predicted by Callaway in 1959 [40]. The details of this model are described elsewhere [40,41]. The expression for κL is given as follows [40]Figure 5


Effect of grain size on thermal transport in post-annealed antimony telluride thin films.

Park NW, Lee WY, Hong JE, Park TH, Yoon SG, Im H, Kim HS, Lee SK - Nanoscale Res Lett (2015)

Measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3thin films. (a) Measured total thermal conductivity, κf = κL + κe, of 400-nm-thick Sb2Te3 films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C as a function of temperature. (b) Measured total thermal conductivity of film annealed at 300°C as a function of temperature (red in scatter plot). For comparison, the theoretically calculated total thermal conductivity (κf, solid line in red) with the two components of the thermal conductivity (the electronic (κe, dotted line in black) and lattice thermal conductivities (κL, solid line in blue)), are also included. κe was calculated from the out-of-plane electrical conductivity using the Wiedemann-Franz law.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4384892&req=5

Fig5: Measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3thin films. (a) Measured total thermal conductivity, κf = κL + κe, of 400-nm-thick Sb2Te3 films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C as a function of temperature. (b) Measured total thermal conductivity of film annealed at 300°C as a function of temperature (red in scatter plot). For comparison, the theoretically calculated total thermal conductivity (κf, solid line in red) with the two components of the thermal conductivity (the electronic (κe, dotted line in black) and lattice thermal conductivities (κL, solid line in blue)), are also included. κe was calculated from the out-of-plane electrical conductivity using the Wiedemann-Franz law.
Mentions: Figure 5a shows the measured out-of-plane total thermal conductivity of the 400-nm-thick Sb2Te3 thin films as a function of temperature, from 20 to 300 K. As shown in Figure 5a, we found that the thermal conductivity of the films exhibits a strong dependence on the annealing temperature and grain-size in the 20 to 300 K temperature ranges. The observed reduction in the temperature-dependent total thermal conductivity was due to enhanced phonon boundary scattering following the decrease in grain size, as has been reported previously [16,35]. From Figure 5a, it can be seen that the total thermal conductivity decreases constantly after the approximately 50 K peak (the so-called ‘Umklapp peak’) has been reached, since the thin films at these temperatures are more significantly affected by phonon-phonon Umklapp scattering. For further understanding of lattice and electronic contribution in total thermal conductivity, we investigated a phonon transport model, which is based on the relaxation time and was previously predicted by Callaway in 1959 [40]. The details of this model are described elsewhere [40,41]. The expression for κL is given as follows [40]Figure 5

Bottom Line: The measured total thermal conductivities of 400-nm-thick thin films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C were determined to be 2.0 to 3.7 W/m · K in the 20 to 300 K temperature range.We found that the film grain size, rather than the strain, had the most prominent effect on the reduction of the total thermal conductivity.To confirm the effect of grain size on temperature-dependent thermal transport in the thin films, the experimental results were analyzed using a modified Callaway model approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea.

ABSTRACT
The effects of grain size and strain on the temperature-dependent thermal transport of antimony telluride (Sb2Te3) thin films, controlled using post-annealing temperatures of 200°C to 350°C, were investigated using the 3-omega method. The measured total thermal conductivities of 400-nm-thick thin films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C were determined to be 2.0 to 3.7 W/m · K in the 20 to 300 K temperature range. We found that the film grain size, rather than the strain, had the most prominent effect on the reduction of the total thermal conductivity. To confirm the effect of grain size on temperature-dependent thermal transport in the thin films, the experimental results were analyzed using a modified Callaway model approach.

No MeSH data available.


Related in: MedlinePlus