Near-bulk resistivity of sub-10nm Au films by breaking free from thickness downscaling effects

Abstract

The miniaturization of electronic devices requires thin films with electrical conductivities that are comparable to those of bulk metals. However, ultrathin coinage metal films inevitably suffer from increased electrical resistivity compared with bulk metals, hindering their performance in miniaturized electronics. This study presents a novel approach to achieve near-bulk resistivity in sub-10-nm-thick Au films on heterogeneous oxide substrates. Our method utilizes O-incorporated epitaxial growth of Au films on α-Al2O3(0001) substrates followed by thermal treatment. This strategy promoted an exceptional film crystallinity, particularly favoring the Au(111) orientation, and significantly reduced the resistivity. Notably, the 8-nm-thick Au film exhibited a record-low resistivity of 3.7 μΩ⋅cm, approaching that of a significantly thicker (60-nm) Au film. This performance surpasses those of Cu and Ag film electrodes of similar thicknesses. Density functional theory calculations provided theoretical insights into the mechanism of O-induced epitaxial growth. Our findings demonstrate that improved crystallinity mitigates the strong dependence of resistivity on the thickness reduction. This study challenges the conventional view of resistivity increase in ultrathin metal films and offers a promising path toward high-performance miniaturized electronics with superior electrical properties.