Research

The objectives of the MuTT Lab are to (1) develop tools for studying microscale thermal transport phenomena (2) develop new materials which push the limits of achievable transport properties (thermal conductivity, interface conductance, heat capacity, thermoelectric power factor), and (3) to develop new device technologies based on these materials.  Applications areas include the cooling of electronic devices, energy efficiency, thermoelectric energy conversion, and next-generation magnetic recording devices.

One of the more advanced tools being built in our lab is a state-of-the-art time-domain thermoreflectance system.  The system utilizes femtosecond lasers to measure the through-plane thermal conductivities of thin film materials (from monolayer to bulk through-plane measurements) with a spatial resolution in the range of 1 micron.  The TDTR system can also utilize picosecond acoustic reflection for the determination of geometric or elastic properties of subsurface layers.  Recent advances also make it possible to measure the in-plane thermal conductivity of thin films using small spot sizes.  By performing experiments at very high speed, it is not only possible to confine heat to a very thin layer near the surface, but one can also induce temperature gradients so steep that Fourier’s law is broken.  Because these effects are related to the finite time/length-scales of heat carrier scattering, this allows us to directly probe the microscale processes responsible for transport properties.

Time Domain Thermoreflectance (Image from Kang et al, "Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters,"  Rev. Sci. Instr., 11, 114901, 2008)

Time Domain Thermoreflectance (Image from Kang et al, “Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters,” Rev. Sci. Instr., 11, 114901, 2008)