Controllable Seebeck Coefficients of a Metal-Diffused Aluminum Oxide Layer via Conducting Filament Density and Energy Filtering

We investigate the intrinsic thermoelectric (TE) properties of the metal-diffused aluminum oxide (AO) layer in metal/AO/metal structures, where the metallic conducting filaments (CFs) were locally formed in the structures via an electrical breakdown (EBD) process as shown by resistive switching memory devices, by directly measuring cross-plane Seebeck coefficients on the CF-containing insulating AO layers. The results showed that the Seebeck coefficients of the CF-containing AO layer in metal/AO/metal structures were influenced by the generation of the metallic CFs, which is due to the diffusion of the metal into the insulating AO layers when exposed to a temperature gradient in the direction of the cross plane of the sample. In addition, the increase in the Seebeck coefficients of the CF-containing AO layer when the number of EBD-processed patterns was increased is satisfactorily explained by the low-energy carrier (i.e., minority carriers) filtering through the metal-oxide interfacial barriers in the metal/AO/metal structures.