title: Significant reduction of thermal conductivity in Si/Ge core-shell nanowires.
abstract: We report on the effect of germanium (Ge) coatings on the thermal transport properties of silicon (Si) nanowires using nonequilibrium molecular dynamics simulations. Our results show that a simple deposition of a Ge shell of only 1 to 2 unit cells in thickness on a single crystalline Si nanowire can lead to a dramatic 75% decrease in thermal conductivity at room temperature compared to an uncoated Si nanowire. By analyzing the vibrational density states of phonons and the participation ratio of each specific mode, we demonstrate that the reduction in the thermal conductivity of Si/Ge core-shell nanowire stems from the depression and localization of long-wavelength phonon modes at the Si/Ge interface and of high frequency nonpropagating diffusive modes.
authors.affiliation: Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland. hum@ethz.ch
authors.forename: Ming
authors.initials: M
authors.lastname: Hu
authors.forename: Konstantinos P
authors.initials: KP
authors.lastname: Giapis
authors.forename: Javier V
authors.initials: JV
authors.lastname: Goicochea
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Zhang
authors.forename: Dimos
authors.initials: D
authors.lastname: Poulikakos
mesh_terms: D003460:Crystallization / Q000379:methods*; D005857:Germanium / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D016062:Porosity; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D013814:Thermal Conductivity
chemical_list: D046911:Macromolecular Substances; D005857:Germanium; D012825:Silicon