Energy Transport for Nanostructured Materials

At the nanoscale, interfaces and boundaries can strongly suppress the energy transport by scattering heat and/or charge carriers. The importance of such energy transport processes can be found in many applications, such as thermal management of optical and electronic devices, thermoelectric materials for energy conversion, thermal insulation materials for energy conservation, thermal interface materials using nanostructures, high-performance and thermally safe batteries, thermal therapies with nanoparticles, and nanostructure-based electronic devices. A better understanding of how carriers interact with an interface or boundary can largely advance the applications of nanotechology in many research fields. Due to the complexity of real interfaces and boundaries, however, such understanding is still in its infancy after decades of research.

In this Research Topic, we invite scholars to contribute original research articles as well as review articles that will stimulate the continuous studies on energy transport at the nanoscale. Potential topics include but are not limited to:

• Experimental and theoretical studies of a grain boundary (within a bulk material, a thin film, or or an atomic-thick material) or general heterojunction for its energy-dependent transmission and reflection of incident phonons that are the dominant heat carriers in nonmetallic materials. Atomistic simulations, particularly those using first-principles interatomic force constants, are encouraged. Experimental studies may also focus on the comparison of interfacial phonon transport for materials synthesized by different techniques (e.g. chemical vapor deposition, hydrothermal coating, hot press) and synthesis conditions (e.g., temperature, ultrahigh pressure, and post-process annealing).
• Experimental and/or theoretical studies of thermal transport across a metal-nonmetal interface, where the dominant heat carriers are changed from electrons in a metal to phonons in a crystal, or non-propagating diffusive modes in polymers or glasses. Studies on detailed electron-phonon interactions near the interface are of particular interests.
• Transport properties of various nanostructures (e.g. nanowires, nanoporous films) to reveal how surface scattering may affect electron and phonon transport.
• Fundamental studies to elucidate and further engineer the energy transport processes through the contact between 1) a nanostructure and a surface or metal junction, or 2) nanostructures (e.g., stacked atomic-thick materials, bundled nanowires, welded nanostructures, entangled carbon nanotubes). The latter may also be focused on electron transport. New approaches to improve these contacts are highly encouraged for submission.
• Studies on the thermal interface between a thin film and its grown substrate, or the bonding between a thin film and a wafer (e.g., GaN bonded onto a diamond substrate). Studies on “interface engineering” to facilitate the thermal transport across these interfaces is encouraged.
• Charge transport across the interface between an electrode material and the solid/liquid electrolyte within a battery, which also involves heat generation. Attention should also be paid to further engineering such an interface to improve the battery performance.
• Theoretical model studies on the thermal interface conductance, which would be more developed than the widely used acoustic and diffuse mismatch models.