Seebeck Coefficient Effects of Nanoscale Conductors in a Gaseous Flow Environment
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Seebeck Coefficient Effects of Nanoscale Conductors in a Gaseous Flow Environment Patrick L. Garrity1 and Kevin L. Stokes2 1
Loyola University New Orleans, Department of Physics, 6363 St. Charles Ave., New Orleans, LA 70118, USA 2 Advanced Materials Research Institute, University of New Orleans Lakefront, New Orleans, LA 70148, USA
ABSTRACT The surrounding ambient introduces a gaseous boundary to many potential nanotechnology applications such as nanoscale thermoelectric devices and low dimensional thermal control devices. Despite the large surface area to volume ratio of nanostructures, a formal study of the surface scattering effects induced by a gaseous boundary has received little attention. In this work, we consider the perturbing effects to the electron cloud or jellium of conducting nanostructures when submitted to a gaseous interface of varying interaction energies. Specifically, we incorporate the novel experimental method of Dynamic Electron Scattering (DES) to measure the Seebeck coefficient of 30 nm thick Au and Cu metal films in He and Ar atmospheres. The gas particle impact energy is varied by changing the flow speed from stationary (non-moving gas field) to high speed flow over the metal films. The scattering effects of each gas are clearly observable through a Seebeck coefficient increase as the gas impact energy increases. We find the high collision density of He to induce a greater increase in thermopower than the much heavier Ar with lower collision density. The perturbed transport properties of the Au and Cu thin films are explained by kinetic surface scattering mechanisms that dominate the scattering landscape of high surface area to volume ratio materials as suggested by comparative measurements on bulk Cu. INTRODUCTION Unlike the well studied area of chemical and physical adsorption of gas particles at a solid surface [1-3], the perturbed thermal, electrical and thermoelectric transport properties incurred by a solid conductor due to kinetic gaseous surface scattering interactions has received little attention. The closest relevant work in this area has occurred primarily in the surface science community with regards to helium atom scattering (HAS) spectroscopy [1]. Comprehensive studies have appeared in the literature on HAS induced by the crystal lattice surface or electron jellium in an effort to understand the HAS spectroscopic results [4,5]. It should be made clear however, that these reports investigate the scattering effects occurring in the helium gas field and do not encompass the scattering effects on the solid material. The scattering effects of the solid become especially important in the nanoscale regime where large surface area to volume ratios indicate the potential dominance of surface perturbations within the overall scattering landscape. Within the few reports available, one group reported thermoelectric and resistivity coefficient
changes in carbon nanotubes under different gaseous environments and attempted to explain the effect by assuming “dents” were formed in the na
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