纳米Pt膜的晶粒尺寸及其对热导率的影响

GRAIN SIZE AND ITS EFFECT ON THERMAL CONDUCTIVITY OF Pt NANOFILMS

采用电子束-物理气相沉积法(EB-PVD)制备了6个厚度为15-62 nm的铂薄膜,研究了纳米薄膜的晶粒尺寸及其对热导率的影响规律．当薄膜厚度小于30 nm时,晶粒平均尺寸接近于薄膜的厚度;晶粒尺寸随着薄膜厚度的增加而增大并趋于定值;当薄膜厚度大于30 nm时,晶粒尺寸约为20 nm．受薄膜的表面和内部晶界的综合影响,铂纳米薄膜的热导率大大低于体材料的值,并且纳米薄膜的热导率随着薄膜厚度的增加而增大并趋于一个低于体材料热导率的值．

Six Pt films with thicknesses of 15-62 nm have been fabricated by electron beamphysical vapor deposition （EB-PVD）. The grain sizes of the Pt nanofilms and its effect on the thermal conductivity have been studied experimentally. It is found that the grain size increases with the nanofilm thickness increasing and goes to a constant about 20 nm. The grain size is nearly comparable with the nanofilm thickness with the thickness less than 30 nm, while becomes much less than the nanofilm thickness with the thickness larger than 30 nm. Influenced by the surface and grain boundary effects, the thermal conductivity of the Pt nanofilms is greatly lower than that of the Pt bulk. It is noted that the thermal conductivity of the studied platinum nanofilms increases with the thickness increasing and runs to 35 W/mK, which is much lower than that of the bulk material.