Phonon Transport and Thermoelectricity in Defect-Engineered InAs Nanowires

Abstract

There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiN x membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature.

Intrinsic nanotwin effect on thermal boundary conductance in bulk and single-nanowire twinning superlattices

“…Also, Dong et al [32] have recently found a weak dependence of thermal boundary resistance from TBs in nanotwinned diamond by MD. However, these atomistic predictions contradict recent experiments in InP and Ge twinned NWs finding up to 50% reduction in thermal conductivity attributed to nanotwin effects [33,34], proving that the role of twin size on heat conduction is not clearly understood. Here, we report atomistic simulations showing evidence for an intrinsic nanotwin effect on thermal conductivity and twin boundary conductance in bulk and small-scale (NW) twinning superlattices in pure Si.…”

Twinning Superlattice Formation in GaAs Nanowires

“…33À38 A reduction in thermal conductivity, which has been both modeled 39À41 and demonstrated, 42 holds further interest for thermoelectric application, while increased mechanical strength has been reported for twinned metallic nanowires 43,44 Periodic twin plane formation in IIIÀV nanowires has been widely reported to be promoted by zinc doping. 3,19,20,22,23,45 In their pioneering work on twinning superlattice formation in InP nanowires, Algra et al 19 discussed several possible actions of this impurity.…”

Phonon transport across crystal-phase interfaces and twin boundaries in semiconducting nanowires

“…Understanding heat transport in these systems is important both for fundamental reasons and with a view to applications. 9,10 On the one hand, phonon scattering at crystal-phase interfaces and, particularly, twin boundaries defies many phenomenological models used to account for interface thermal resistance; on the other hand, crystal-phase engineering can be used to design materials with tailor-made properties 3,[11][12][13][14][15] and twinning superlattices are playing an increasingly important role in nanowire science. [16][17][18][19] In this work we use both state-of-the-art nonequilibrium Green's functions (NEGF) and nonequilibrium molecular dynamics (NEMD), based on carefully parameterized interatomic potentials, to calculate the TBR of a few prototypical homojunctions, compare them with the values obtained in similar, conventional heterojunctions and elucidate the atomic-scale mechanisms that originate interface scattering.…”