AVS 50th International Symposium
    Nanometer Structures Tuesday Sessions
       Session NS-TuM

Paper NS-TuM11
Theoretical Calculation of the Thermal Conductivity of Semiconducting Nanowires

Tuesday, November 4, 2003, 11:40 am, Room 308

Session: Nanowires
Presenter: N. Mingo, NASA-Ames Research Center
Authors: N. Mingo, NASA-Ames Research Center
L. Yang, NASA-Ames Research Center
Correspondent: Click to Email
An atomistic Green function theoretical formalism to compute phonon transport in nanostructures will be presented, and its application to several different problems will be discussed. In particular, we present calculations of the thermal conductivity of Si and Ge nanowires, and compare these with some experimental results [D. Li et al., submitted]. One important problem that has not yet been extensively studied in an atomistic framework, is that of ballistic vs. diffussive phonon transport. Using our atomistic Green function approach, we study the transition from ballistic to diffusive phonon transport, occuring as the system's length increases. The way in which this transition takes place is largely determined by properties of its boundary. We will discuss the ballistic-diffusive transition in terms of atomic properties of the wire and its coating. Differences between (111) and (110) orientated nanowires are shown to be of more importance in the ballistic regime than in the diffusive one. Finally, a two parameter model, with the parameters depending only on bulk material properties, is also derived. Using this method we obtained good predictive calculations of the thermal conductivity of Si nanowires. The method employs the full phonon dispersion relations of bulk Si. The relative importance of specific nanowire modes not present in bulk, as the system's size becomes smaller, will be discussed. The results and methods presented offer an exciting new range of possibilities in the study and development of thermal transport through nanosized devices.