Measurement of heat transfer in sub-micron area of thin films by transmission electron microscope

利用透射电子显微镜（TEM）的高空间分辨率（-nm），研究了一种测量薄膜热导率的方法，并将其应用于厚度为30- 300 nm的多晶薄膜，通过薄膜的电子被晶格的热振动散射，TEM图像上的电子束强度随样品温度的变化而变化。当激光束聚焦在薄膜上时，薄膜可以被局部、快速和重复地加热。在透射电镜上安装了一个带有振幅调制器的He-Ne激光器和一个聚焦和准直的光学系统，将10 mW左右的激光束聚焦到直径为10- 20 μ m的样品上。用闪烁体和光电倍增管观察样品的放大像，并在样品上测量小范围内（1 μ m）的光束强度，利用热容和热扩散率延迟薄膜温度的上升。将相位差转换为热导率。制备了不同厚度的真空沉积膜（Al，Sn，Ni，Ge，Cu，Mg，Bi），并进行了测量。在大多数情况下，薄膜电导率为体电导率的30-80%，并随着晶粒尺寸的增加而接近体电导率。在工程实施过程中，我们还没有完成传热与晶体结构之间关系的研究。这将被连续研究。

With the high-spatial resolution (-nm) of transmission electron microscopes(TEM), a measurement method of thermal conductivity of thin films is investigated and it is applied to polycrystalline films whose thickness is 30-300nm.Electrons through a film are scattered by the thermal vibration of lattice and the beam intensity at TEM image changes by the temperature of the specimen. When the laser beam is focused on a film, the film can be heated locally, quickly and repeatedly. combining these functions, we can investigate the mechanize of heat transfer in this films.A He-Ne gas laser with amplitude modulator and an optical system for focusing and aligning are attached to the TEM.The laser beam with about 10mW is focused on the specimen to the area of 10-20mum in diameter. The magnified image of the specimen is observed and the beam intensity in a small area (1mumphi on specimen) is detected by a scintillator and a photo-multiplier.The rise of film temperature is delayd to the laser power by the heat capacity and heat diffusivity. The phase difference is converted to the thermal conductivity. Then, this method has advantage that the deduction is independent to the absolute temperature and the film thickness.Some vacuum-deposited films (Al, Sn, Ni, Ge, Cu, Mg, Bi) with various thicknesses are prepared and measured. In most cases, film conductivity is in 30-80% of bulk conductivity and approaches to it as the grain size increases. The film conductivity reduces as the thickness decreases.In the term of project, we have not finished the investigation to the relation between heat transfer and crystal structure. This will be studied in succession.