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Coherent phonon scattering effects on thermal transport in thin semiconductor nanowires

2007; American Physical Society; Volume: 76; Issue: 15 Linguagem: Inglês

10.1103/physrevb.76.155313

1550-235X

Pádraig Murphy, Joel E. Moore,

Quantum and electron transport phenomena

The thermal conductance by phonons of a quasi-one-dimensional solid with isotope or defect scattering is studied using the Landauer formalism for thermal transport. The conductance shows a crossover from localized to Ohmic behavior, just as for electrons; however, the nature of this crossover is modified by delocalization of phonons at low frequency. A scalable numerical transfer-matrix technique is developed and applied to model quasi-one-dimensional systems in order to confirm simple analytic predictions. We argue that existing thermal conductivity data on semiconductor nanowires, showing an unexpected linear temperature dependence, can be understood through a model that combines incoherent surface scattering for short-wavelength phonons with nearly ballistic long-wavelength phonons. It is also found that even when strong phonon localization effects would be observed if defects are distributed throughout the wire, localization effects are much weaker when defects are only at the boundary, as in current experiments.