Nanowire Composite Thermoelectric Devices

Abstract

This paper discusses the design, fabrication and testing of a novel thermoelectric device comprised of arrays of silicon nanowires embedded in a polymer matrix. By exploiting the low thermal conductivity of the composite and presumably high power factor of the nanowires, a high figure of merit should result. Arrays were first synthesized using a vapor-liquid-solid (VLS) process leading to one-dimensional growth of single-crystalline nanowires. To provide both structural support and thermal isolation between nanowires, parylene, a low thermal conductivity and extremely conformal polymer, was embedded within the arrays. Mechanical polishing and oxygen plasma etching techniques were used to expose the nanowire tips and a metal contact was deposited on the top surface. Scanning electron microscopy pictures illustrate the results of the fabrication processes. Using the 3ω technique, the effective thermal conductivity of the nanowire matrix was measured.

Fabrication and thermoelectrical characterization of three‐dimensional nanowire networks

“…The homogeneity of the growth of Sb nanowires by pulsed deposition with the experimental conditions mentioned above was further investigated by high resolution scanning electron microscopy (HRSEM) (JEOL JSM 7401F). Figure shows a series of HRSEM images of the top surface of a polymer membrane (∼10 8 pores cm −2 ) after the growth of parallel arrays of Sb nanowires (a) as grown (after removal of deposited caps) and (b–d) after removing the PC selectively by reactive ion etching (RIE) (Vacutec AB1500 Plasma System), using an oxygen plasma . After 1, 2, and 3 min of etching, 0.5, 1, and 1.5 μm of PC were removed from the top layer, respectively.…”

Generalized equation of phonon radiative transport

“…This situation is similar to scattering EM waves by fibers, which is highly anisotropic and asymmetrical. 15 Heat transfer in the nanowire will be ballistic at low temperatures and the scattering will be highly anisotropic and asymmetrical. Scattering by a nanoparticle can be highly anisotropic and asymmetrical depending on the acoustic mismatch with the host medium.…”

Thermopower measurement of freestanding nanowires using a MEMS workbench

“…Several groups have chosen to measure the aggregate thermoelectric effect of an array of nanowires in a matrix of a different material [10][11][12][13][17][18]. This technique precludes any controlled studies as a function of size, impurities etc, since in an ensemble of such nanowires any specific effects will average out.…”