Title: Electrical Resistance in All-metallic Cluster of Ultra-small Silver Nanoparticles Embedded in Gold

Speaker: Dr. Tuhin Kumar Maji, IISc, Bangalore

Abstract: Ultra-small nanoparticles of noble metals, in particular silver (Ag) or gold (Au), have been extensively investigated for their optical, magnetic, chemical, and physical properties. However, putting such structures together in an electrically conducting metallic matrix, where the physical size of each individual nanoparticle is crucial, has proven to be difficult. This is because tunnel barriers caused by surface-protecting ligands, oxidation, etc. frequently hinder real metallic conduction through single or clusters of metallic nanoparticles. These difficulties have been resolved in a cross-linked nanohybrid assembly made of extremely small silver nanoparticles (AgNPs) in an all-metallic matrix of Au by removing the chemical residues. The resulting Ag-Au nanohybrid exhibits metallic behavior where the resistance decreases with decreasing temperature, for all radii (rAg ≈ 1 − 3 nm) and concentrations of AgNPs (average center-to-center distance between two AgNPs d ≈ 4 − 6 nm) from room to cryogenic temperatures (≈ 6 K). Surprisingly, we find that the hybrid's electrical resistivity scales directly with the net surface area of the implanted AgNPs, leading to residual resistivity up to 40 µΩ.m, which is more than two orders of magnitude higher than that of crystalline Au. Our study presents a novel strategy for designing nanostructured metals with precisely controllable electrical transport characteristics.

Ref: Maji et al. *ACS Appl. Electron. Mater.* 2023, 5, 5, 2893–2901