High temperature TDTR up to 1000 K using HfN transducers: Paper published in Appl. Phys. Lett – Congrats Tina!

Dr. Tina Rost’s work has recently appeared in Applied Physics Letters.

Rost, C.M., Braun, J.L., Ferri, K., Backman, L., Giri, A., Opila, E., Maria, J.-P., Hopkins, P.E., “Hafnium nitride films for thermoreflectance transducers at high temperatures: Potential based on heating from laser absorption,” Applied Physics Letters 111, 151902 (2017). PDF.

In a typical TDTR experiment, a thin metal transducer is deposited on top of a sample to measure the sample’s thermal properties.  Ultimately, TDTR can be limited by the stability of this transducer.  In this work, we have demonstrated the ability to extend TDTR measurements up to 1000 K using HfN as a metal transducer.  Note only does HfN demonstrate one of the highest thermoreflectance coefficients at 800 nm measured to date, but it’s high temperature phase stability make it attractive for use as a metal transducer at high temperatures.

Abstract

Time domain thermoreflectance (TDTR) and frequency domain thermoreflectance (FDTR) are common pump-probe techniques that are used to measure the thermal properties of materials. At elevated temperatures, transducers used in these techniques can become limited by melting or other phase transitions. In this work, time domain thermoreflectance is used to determine the viability of HfN thin film transducers grown on SiO2 through measurements of the SiO2 thermal conductivity up to approximately 1000 K. Further, the reliability of HfN as a transducer is determined by measuring the thermal conductivities of MgO, Al2O3, and diamond at room temperature. The thermoreflectance coefficient of HfN was found to be 1.4 10^-4 K^-1 at 800 nm, one of the highest thermoreflectance coefficients measured at this standard TDTR probe wavelength. Additionally, the high absorption of HfN at 400 nm is shown to enable reliable laser heating to elevate the sample temperature during a measurement, relative to other transducers.

We acknowledge the financial support from the Office of Naval Research MURI program (Grant No. N00014-15-1- 2863).