CAREER: Nanoscale temperature mapping across interfaces using scanning transmission electron microscopy

William Marsh Rice University, Houston TX

Investigators

Abstract

Interfaces between materials pose a major barrier to the thermal management of nanotechnologies ranging from transistors to light-emitting diodes and heat-assisted magnetic recording devices. Improvements in the fundamental understanding of nanoscale heat flow mechanisms across these interfaces could allow engineers to tailor the composition and structure of interfaces for optimized cooling strategies, leading to improved device durability and efficiency. However, it is currently difficult to test the predictions of competing interfacial thermal transport theories at the nanoscale because thermal experiments are not able to map temperature at the relevant near-atomistic lengthscales. This work will develop scanning transmission electron microscopy nanothermometry experiments and use atomistic calculations to elucidate the mechanisms of interfacial thermal transport and to provide high spatial resolution insight into the interface structure-thermal property relationship. This project will also build upon existing collaborations between Rice University and Houston-area community colleges to implement summer research experiences for community college students and to develop outreach events that promote career opportunities in nanotechnology and thermal management. The goal of this project is to test models for interfacial phonon heat transport by mapping temperature with sub-nanometer spatial resolution across strongly bonded interfaces. The nanothermometry measurements will leverage the temperature-dependent thermal diffuse scattering that has been detected in scanning transmission electron microscopy diffraction patterns and annular dark field images. This thermal diffuse scattering is directly related to the local atomic vibration amplitudes, which increase with increasing temperature. Calibrating and mapping the thermal diffuse scattering as a function of beam position will allow experiments with sub-nanometer electron beam diameters to measure the temperature profile with ultrahigh spatial resolution. These thermal electron microscopy experiments will be compared with theoretical predictions by combining atomistic modeling of temperature-dependent atomic vibrations near interfaces with multislice electron diffraction calculations to quantify the thermal diffuse scattering. The results will provide insight into the underlying physical mechanisms of interfacial thermal transport across semiconductor-semiconductor and semiconductor-metal junctions. Future application of this fundamental knowledge could allow engineers to improve the thermal design of interfaces in nanoelectronics and information storage technologies, with the goal of enabling more efficient device performance. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.