Studying thermal conductivity after irradiation

Controlling the thermal conductivity of materials can tailor them for various thermal management applications. One way to adjust thermal transport properties is to bombard a material with high energy particles. While in general this method damages the material, irradiation with swift heavy ions (SHI) forms an aligned array of ion tracks, altering thermal conductivity.

Abdullaev et al. investigated this method by determining how ion tracks from SHI irradiation modified thermal conductivity in sapphire samples. The authors used time-domain thermoreflectance (TDTR) – a non-contact, laser-based technique – to measure the variation in thermal conductivity.

The authors identified two regions with distinct reduced thermal conductivity values consistent with thermal transport models. One is an ion track region that is several micrometers thick. The other is an amorphous layer that only forms with high dose irradiation, and is several tens of nanometers thick. They confirmed the existence of these two regions with high resolution electron microscopy.

“This study addresses the knowledge gap in understanding the effect of SHI irradiation on thermal transport,” said author Zhandos Utegulov.

Their results also demonstrate TDTR’s capability to measure ion damaged materials’ thermal transport behavior on the nanometer scale. This technique could aid in future studies of irradiated materials’ nanoscale and microscale thermal transport properties.

“Our work is important for further investigation in the general field of ion beam modification where electronic, optical, electrochemical and thermal transport properties of insulating, dielectric, semiconductors and ceramics are tailored to meet the requirements of their respective applications,” said author Marat Khafizov.

Source: “Thermal transport across nanoscale damage profile in sapphire irradiated by swift heavy ions,” by A. Abdullaev, V. S. Chauhan, B. Muminov, J. O’Connell, V. A. Skuratov, M. Khafizov, and Z. N. Utegulov, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5126413 .