Controllable fabrication of Au-nanoprotrusion arrays as a platform for the materials design and characterization

Abstract

Au-nanoprotrusions (AuNPs) were fabricated on a gold substrate using obliquely incident Ar+ ions with a simultaneous supply of carbon at room temperature. The sputter erosion rate was kept almost constant at 49 nm/min, while the deposition rate of carbon ranged from 1.2 to 0.6 nm/min. Scanning electron microscopy (SEM) observation revealed the variation in the number density and shape of the AuNPs ranging from slender needles to cones with a large apex angle, depending on the carbon deposition rate. Transmission electron microscopy (TEM) demonstrated that the slender needles were characterized by the bi-metal like structure of the large Au grain-rich phase and amorphous carbon phase with a dispersion of fine Au nanoparticles, while the conical structures consisted of Au grains with an amorphous carbon cap region on top. Those structures were selectively prepared, depending on the application. Li-C nanocomposite films deposited on conical structures, for instance, were readily observed cross-sectionally by TEM without any post treatment, revealing the instantaneous formation of a solid electrolyte interphase (SEI) after only 2 charge-discharge cycles in the cyclic voltammetry (CV) measurement. Thus, AuNPs are promising as a platform for the materials design and characterization in atomic dimensions.