Abstract
In this paper, we report the results of slight changes in the thermopower of long W, Mo, Zn, Cu, brass, and Ti wires, that resulted from changes in the wire’s diameter or cross-sectional area. The samples used in the tests had a round shape with a diameter that ranged from tens of micron to 2 mm, which was much larger than the corresponding mean free paths of these materials. Nevertheless, a small change in thermopower, at the order of 1–10 nV/K, was repeatedly observed when the wire diameter was changed, or when the cross-sectional area of the wire was altered by mechanical methods, such as grinding or splitting. The results are consistent with previous observations showing that the thermopower in metallic thin film stripes changes with their width, from 100 μm to as little as 70 nm, implying a universal, geometric-boundary-related size effect of thermopower in metal materials, that occurs at the nanometer scale and continuously decreases all the way to the millimeter scale. This effect could be applied in the manufacturing of high-temperature sensors with simple structures.
Highlights
Metals and metallic alloys are important functional materials for modern devices and electronic systems
It is known that, when the thickness of a metallic thin film is less than 100 nm, which is comparable to the mean free path of electrons in a metal, a strong thickness-dependent effect occurs in the scattering processes of electron-electron and electron-phonon interactions, resulting in a drastic reduction of conductivity when the film thickness further decreases [23]
Equation (1) leads to a rough relation of (Sf − Sbulk ) ∝ 1/t. This well-developed theory has been successfully applied to the description of experimental data on the thickness dependence of the thermopower of a variety of metallic films [23,24,25,26], as well as the results of enhanced ZT in patterned
Summary
Metals and metallic alloys are important functional materials for modern devices and electronic systems. It is known that, when the thickness of a metallic thin film is less than 100 nm, which is comparable to the mean free path of electrons in a metal, a strong thickness-dependent effect occurs in the scattering processes of electron-electron and electron-phonon interactions, resulting in a drastic reduction of conductivity when the film thickness further decreases [23] This effect becomes one of the critical issues in design and fabrication of interconnects in the latest large-scale integrated circuits [1]. Equation (1) leads to a rough relation of (Sf − Sbulk ) ∝ 1/t This well-developed theory has been successfully applied to the description of experimental data on the thickness dependence of the thermopower of a variety of metallic films [23,24,25,26], as well as the results of enhanced ZT in patterned. The results indicate a universal size effect of thermopower in metal materials that occurs at the nanoscale, and decreases, but continues to exist, from the nanoscale up to the millimeter scale
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