Phononics in Low-dimensions: Engineering Phonons in Nanostructures and Graphene

Phonons – quanta of crystal lattice vibrations – reveal themselves in all electrical, thermal and optical phenomena in materials. Nanostructures open exciting opportunities for tuning the phonon energy spectrum and related properties of materials for specific applications. A recent advent of graphene and quasi two-dimensional materials increased the possibilities for controlled modification of the phonon spectrum and phonon transport – referred to as phononics or phonon engineering – even further. Acoustic phonons are the main heat carriers in graphene while optical phonons are used for determining the number of atomic planes in the few-layer graphene via Raman spectroscopy. Uniqueness of phonon transport in two dimensions translates to unusual thermal properties, which can be altered more drastically than in corresponding bulk crystals. We outline the general concept of phonon engineering in nanostructured materials and describe methods of tuning the phonon spectrum and transport in graphene and quasi 2-D materials. Control of thermal properties in graphene via ribbon edges, isotope composition, grain boundary and defect engineering, phonon rectification and atomic-plane orientation are discussed.