Thin Film Non-Noble Transition Metal Thermophysical Properties

The transient thermoreflectance (TTR) technique coupled with a pump-probe experimental setup enables the observation of thermal transport phenomena on a sub-picosecond time scale. The reflectance from non-noble transition metals (at least one unoccupied d-orbital in the conduction band) can be shown to have a linear dependence when compared to small changes in the electron and lattice temperatures. This thermal dependence can be combined with the parabolic two step (PTS) model to enable measurement of the electron-phonon coupling factor and thermal conductivity of thin film materials. Experimental results are presented for thin film samples of the non-noble transition metals platinum and nickel. Results are presented using laser wavelengths ranging from 740 nm to 805 nm and using a range of laser fluences (ranging from ∼0.35 to 2 J/m²). Over this range of wavelengths and fluences the material properties are shown to be independent of the measurement conditions.

Keywords:

• electron-phonon coupling
• thermal conductivity
• nickel
• platinum
• femtosecond
• thin film
• reflectance

The authors are grateful to the National Science Foundation (CTS-9908372) for their financial support.