Thermal conductivity of nanoscale polycrystalline ZnO thin films

Thermal conductivities (TCs) of ZnO thin films of thickness 80–276 nm prepared by sol–gel method are measured by the transient thermoreflectance (TTR) system. The obtained TCs ranging from 1.4 to 6.5 W/m K decrease while the thickness decrease. The measured TCs are much smaller than those of bulk ZnO, which is about 100 W/m K. The possible reasons for the decrease are the grain boundary and defects. The latter is the dominating one from the analysis.

Research highlights
► Thermal conductivity of ZnO thin films are much smaller than those of bulk ones.
► We examined the results influenced by grain boundary and defects.
► The latter is the dominating reason from the analysis.