Manipulating phonons at the nanoscale: Impurities and boundaries

Efficiently controlling phonon propagation is important in many applications, ranging from the design of thermoelectric materials to thermal budget engineering. Phonon manipulation, nonetheless, has proved to be an elusive task. Here, we review some basic strategies to alter vibrational modes throughout the entire phonon spectrum by means of point and extended defects, boundaries, and design of periodic superstructures. These individual scattering mechanisms allow altering the phononic properties in specific spectral regions; combining two or more can lead to a modification of the full-spectrum.