Surface Phonon

Surface Phonon

In solid state physics, surface phonons are particular lattice vibration modes associated with surfaces. They are an artifact of periodicity, symmetry, and the termination of bulk crystal structure associated with the surface layer of a solid. Knowledge of surface phonon dispersion gives important information related to the amount of surface relaxation, the existence and distance between an adsorbate and the surface, and information regarding presence, quantity, and type of defects existing on the surface.

Phonons can couple with electrons and affect the electrical and optical properties of devices, which is of particular interest for semiconductor quantum dots. The decreasing size of CdSe quantum dots was found to result in increasing surface phonon frequency, which can couple with electrons and affect their properties.

Two methods are used for modeling surface phonons. One is the "slab method", which approaches the problem using lattice dynamics for a solid with parallel surfaces, and the other is based on Green’s functions. Which of these approaches is employed is based upon what type of information is required from the computation. For broad surface phonon phenomena, the conventional lattice dynamics method can be used; for the study of lattice defects, resonances, or phonon state density, the Green’s function method yields more useful results.