Shape and Orientation Effects on the Ballistic Phonon Thermal Properties of Ultra-Scaled Si Nanowires
Date of this Version2011
Journal of Applied Physics: Volume 110, Issue 11. doi: 10.1063/1.3662177
The effect of geometrical confinement, atomic position and orientation of Silicon nanowires (SiNWs) on their thermal properties are investigated using the phonon dispersion obtained using a Modified Valence Force Field (MVFF) model. The spe- cific heat (Cv) and the ballistic thermal conductance (κbal) shows anisotropic variation l with changing cross-section shape and size of the SiNWs. The Cv increases with de- creasing cross-section size for all the wires. The triangular wires show the largest Cv due to their highest surface-to-volume ratio. The square wires with  orientation show the maximum κbal since they have the highest number of conducting phonon l modes. At the nano-scale a universal scaling law for both Cv and κbal are obtained l with respect to the number of atoms in the unit cell. This scaling is independent of the shape, size and orientation of the SiNWs revealing a direct correlation of the lattice thermal properties to the atomistic properties of the nanowires. Thus, en- gineering the SiNW cross-section shape, size and orientation open up new ways of tuning the thermal properties at the nanometer regime.
Nanoscience and Nanotechnology