Thermal Conductivity Case Studies | Laser ThermalUsing SSTR to Spatially Isolate Defect Layers on Thin Films

SSTR can measure the thermal conductivity of thin films to isolate the conductivity effects of defect layers from high quality crystalline regimes.

The Challenge

Thin film thermal conductivity is notoriously lower than that of bulk material due to interface and defect effects that impact phonon scattering.  These defects can be spatially heterogeneous or deep under the surface.

The Solution

SSTR offers a unique ability to control the depth to which thermal conductivity is measured, a capability we can leverage to measure the thermal conductivity of thin AlN films while specifically isolating the thermal conductivity in the high-quality region near the top of the film from that of the lower quality nucleation layer near the AlN/substrate interface.

We show that the high-quality top portion of the film has bulk like thermal conductivity (both in plane and cross plane), but once the measurement volume samples the defect nucleation region, the thermal conductivity drops since the crystal quality in this region is poor.  This unique ability to spatially isolate various regions of a sample and measure the thermal conductivity is enabled by SSTR’s ability to dynamically change spot size (and thus control the depth of probe).

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