Evaluation of Thermal Conductivity Characteristics in Polycrystalline Silicon - The Effect of Nanostructure in the Grains

Abstract

We focused on the nanostructure size by changing the additional annealing conditions during poly-Si thin film fabrication with keeping the same grain size, and evaluated the thermal conductivity characteristics of the poly-Si thin film by Raman spectroscopy. Laser-power dependent Raman spectroscopy showed the temperature increase caused by laser heating. The temperature increase of each sample is different depending on the poly-Si fabrication process. It is considered that this temperature change is caused by the increase in the phonon scattering sites inside the grain due to change in the nanostructure sizes. Moreover, it was revealed that the sample with lowest thermal conductivity has the medium nanostructure size. It may need to consider not only the size but also the density of the nanostructure to understand these phenomena. In conclusion, we clearly indicated that not only the average grain size but also the size and density of the nanostructures inside grains should be carefully considered to control thermal conductivities.