A Novel Method for Characterizing In-plane and Out-of-plane Thermal Conductivity of Nanostructured Materials
Physical Sciences : Physics
Available for licensing
- Yaguo Wang, Ph.D. , Mechanical Engineering
- Jihoon Jeong, M.S. , Mechanical Engineering
- Feng He , Mechanical Engineering
For most bulk materials, thermal conductivity along any given direction is the same. Many traditional techniques can measure thermal conductivity in bulk materials, such as the Laser Flash method. However, for nanostructured materials, e.g. nanometer thickness films, in-plane and cross-plane thermal conductivity can be strikingly different. Furthermore, traditional techniques cannot handle samples with micron/nanometer sizes. As a result, there is a keen demand for developing new techniques that are capable of differentiating thermal conductivity along different directions, and to handle samples with micro/nanometer size.
Researchers at The University of Texas at Austin have developed a method based on the pump and probe system of time-domain thermoreflectance which measures the change of reflectance from the surface, under the assumption that the change of temperature at the surface is proportional to the change of reflectance. This method employs a photomask to generate a grating period image on the sample surface of both pump and probe lasers. The technique is able to get signals from many fringes which contain information about both cross-plane and in-plane thermal transport. After gathering the signal, thermal conductivities of the sample are extracted using the two-dimensional thermal transport model.
- Able to provide thermal conductivity along both in-plane and out-of-plane directions
- Low cost of thermal conductivity measurements
- Highly sensitive measurement of thermal properties
- Optical grating image is projected onto sample surface using photomask.
- Objective lens is used to focus diffracted beams onto sample surface.
- This method includes periodic-multiple time-domain thermoreflectance (TDTR).
Thin-film materials are used for a number of applications in several industries, such as photovoltaic cells, semiconductor, MEMS, and electrical and optical coating. The continued expansion of the solar industry is driving thin-film materials demand. This novel approach should be appealing to electronic device manufacturers who are interested in thermal transport properties and thermal energy management in thin film materials. Markets and Markets reports the thin film market value is expected to grow to $10.25B by 2018.