Size effects on the thermal conductivity of polycrystalline platinum nanofilms
Size effects on the thermal conductivity of polycrystalline platinum nanofilms
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DOI：
10.1088/0953-8984/18/34/007
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
Q. Zhang;B. Cao;X. Zhang;M. Fujii;K. Takahashi
中科院分区：
文献类型：
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作者：
Q. Zhang;B. Cao;X. Zhang;M. Fujii;K. Takahashi
研究了多晶铂纳米薄膜面内热导率的表面效应和晶界效应。纳米膜的厚度范围从15.0到63.0 nm，通过X射线衍射测量的平均晶粒尺寸从9.5到26.4 nm变化。通过直接电加热法测量的纳米膜的热导率从本体值大大降低。测量结果与Qiu和Tien模型以及Kumar和Vradis理论的预测值进行了比较。结果表明，热导率的降低主要是由晶界散射引起的，电子撞击晶界的反射系数约为0.35。弛豫时间模型也适用于研究的尺寸效应，以检查是否仍然有效的Matthiessen规则在预测的多晶金属纳米薄膜的面内热导率。结果表明，在只考虑晶界散射和背景散射的情况下，Matthiessen规则仍然有效。如果表面散射，但是，包括在内，从上述其他理论的Matthiessen规则的偏差已被发现。
The surface and grain-boundary effects on the in-plane thermal conductivity of polycrystalline platinum nanofilms have been investigated. The thicknesses of the nanofilms range from 15.0 to 63.0 nm and the mean grain sizes measured by x-ray diffraction vary from 9.5 to 26.4 nm. The thermal conductivities of the nanofilms measured by a direct electrical heating method are greatly reduced from the bulk values. The measured results are compared with the values predicted by the Qiu and Tien model and the Kumar and Vradis theory. It is found that the reduction in the thermal conductivity is mainly caused by grain-boundary scattering and the reflection coefficient of electrons striking the grain boundaries is around 0.35. The relaxation time model is also applied to study the size effects to check whether the Matthiessen rule is still valid in predicting the in-plane thermal conductivity of polycrystalline metallic nanofilms. The results indicate that by considering only grain-boundary scattering and background scattering the Matthiessen rule is still valid. If surface scattering, however, is included, deviations of the Matthiessen rule from other theories mentioned above have been found.