Cross-Plane Thermal Conductivity Measurements in Self-Assembled Nanodielectric Heterostructures

Hybrid inorganic and organic superlattices provide an opportunity to study the dependence of the thermal conductivity on phonon scattering at the boundaries of inorganic thin films and coupling to internal degrees of freedom in self-assembled molecular junctions. In this talk, I would present time domain thermoreflectance (TDTR) measurements of cross plane thermal transport in self assembled nanodielectric (SAND) heterostructures comprised of alternating layers of solution processed ZrO 2 films and a polarizable phosphonic π-electron molecule-PAE, fabricated with ultralow surface roughness. Through rational design of the SANDs, improved electronic transport properties such as charge carrier mobility and hysteresis, threshold voltage, and exceptional electrical capacitance, of field effect transistors (FETs) based on the SANDs have been demonstrated. The SANDs also provide excπellent mechanical flexibility making them suitable for flexible nanoelectronic applications. In our measurements, the ZrO 2 -SAND-n heterostructure (where n is the number of lattice unit cells) is metallized by electron beam lithography, and a two-temperature heat conduction model is fitted to the TDTR measurements obtained in the sample, from which the effective cross -plane thermal conductivity of the SANDs is obtained as a function of n. The best fit cross -plane thermal conductivity of the SANDs is observed to decrease with the number of unit cells, and for four unit cells, the thermal conductivity at room temperature is as low as 0.3 W/m-K. Our measurements suggest that understanding the origin of the ultra -low thermal conductivity of the SANDs and controlling against it may be crucial to realizing the functional performance and reliability of fl exible SAND based FETs in the future.