Session: 10-01 Interactive Presentations

Paper Number: 97401

97401 - Crystalline-Like Thermal Transport in Disordered Interfacial Thin Films 

Thermal transport across thin-films and interfaces is an important characteristic of small-scale electronic devices. In addition, the electronic properties of these thin films are of extra importance for certain devices such as light-emitting diodes (LEDs). An understanding of the balance between the thermal and electronic properties of thin films is key to designing nanodevices that are efficient, tunable, and robust under the thermal load while in operation. Amorphous materials are often used in thin-film applications for their low electrical conductivity, arising from a restricted atomic mobility in the amorphous phase. However, the amorphicity leading to restricted mobility also significantly reduces the thermal conductivity of the material. This so-called “amorphous limit” is among the lowest thermal conductivity of dense solids, excluding the thermal conductivity of polymer-based materials and specially engineered nanostructures, and poses significant issues when adequate heat dissipation is needed. In this work, we study the thermal transport properties of an amorphous silicon thin-film sandwiched between two crystalline leads. When sandwiched between crystalline silicon leads, the amorphous thin film demonstrates crystalline-like temperature dependence of thermal conductivity in the in-plane directions with a two-fold increase over the thermal conductivity of amorphous silicon at low temperatures while the cross-plane thermal conductivity remains independent of temperature. Lattice dynamics (LD) simulations enables the visualization of the phonon eigenvectors of the structure, and demonstrates that the long-wavelength phonons (propagons) traversing in the in-plane direction of the crystalline silicon leads effectively “hosts” propagons traversing in the same direction in the amorphous material. This facilitation of the propagons in the in-plane direction is attributed to be the cause of the crystalline-like temperature dependence of the in-plane thermal conductivity of the amorphous thin-film. Utilizing these results may lead to the creation of electrically resistive thin-films that are also capable of dissipating heat by leveraging a combination of crystalline and amorphous behaviors.

Presenting Author: Jaymes Dionne University of Rhode Island