Improvement on Thermoelectric Characteristics of Layered Nanostructure by Ion Beam Bombardment

Abstract

We made p-type nanoscale super lattice thermoelectric cooling devices which consist of multiple periodic layers of Si1−x Gex / Si, The thickness of each layer ranges between 10 and 50 nm. The super lattice was bombarded by 5 MeV Si ion with different fluencies aiming to form nano-cluster quantum dot structures. We estimated the thermo-electric efficiency of the so fabricated devices, measuring the thin film cross plane thermal conductivity by the 3rd harmonic method, measuring the cross plane Seebeck coefficient, and finally measuring the cross plane electric conductivity before and after ion bombardment. As predicted, the thermo-electric Figure of Merit of the films increases with increasing Si ion fluencies. In addition to the effect of quantum well confinement of the phonon transmission, the nano-scale crystal quantum dots produced by the incident Si beam further adversely affects the thermal conductivity by absorbing and dissipating phonon along the lattice, and therefore further reduces the cross plane thermal conductivity, This process increases the electron density of state therefore increasing Seebeck coefficient, and the electric conductivity.

Surface modification of Si/Ge multi-layers by MeV Si ion bombardment

“…The size of the Si/Ge multilayer thin film for Seebeck coefficient measurement is 2 mm × 7 mm. The experimental setup for Seebeck coefficient measurement was previously reported elsewhere [16]. Fig.…”

Fabrication And Characterization of Thermoelectric Generators From SiGe Thin Films

“…A metal (Au) contact layer was deposited on the SiO 2 substrate before and after the deposition of monolayer SiGe thin film to enable an electrical contact for the Seebeck coefficient measurement. The high energy ion bombardment can produce nanostructures and modify the property of thin films [9,10], resulting in lower thermal conductivity and higher electrical conductivity. While fig.1a shows the film geometry used for the electrical and thermal conductivity measurements, fig.2b shows the film geometry used for Seebeck coefficient measurement.…”

5MeV Si Ion Modification on Thermoelectric SiO2/SiO2+Cu Multilayer Films

“…In previous studies we have demonstrated the improved thermoelectric properties of SiO2 MLs embedded with various nanoparticles, such as Au, Ag and Cu [9][10][11][12]. ML structures are fabricated to reduce the phonon conduction through the sample, thus increasing the figure of merit.…”

“…is the electrical conductivity, T is the absolute temperature, and is the thermal conductivity [10,11]. Increasing S can increase ZT, by increasing , or by decreasing .…”