Monitoring and modeling the deposition of metal nanoparticles on surfaces by impedance

Abstract

The study of metallic nanoparticles (NPs) on surfaces and their properties has become a common subject for a variety of areas. Notably, to exploit the unique intrinsic features of deposited NPs in macroscopic devices, samples with low coverage are required. The electrical characterization techniques have, however, so far been limited to systems near or beyond the percolation limit, when the nanostructure’s resistive behavior is dominant. Here we describe the impedance response of interdigitated electrodes (IDE) during Ag NP deposition, from the very beginning up to the percolation limit. Our experiments present two regimes: up to ~20% of coverage the capacitance grows linearly with the deposition, increasing abruptly afterward. To understand the experimental data, we propose a model in which the capacitance response is attributed to isolated and agglomerated NPs. Initially, isolated NPs contribute to the capacitive response. Beyond ~20% coverage, shielded regions of the IDE due to agglomerated NP islands start to dominate until eventually percolation leads to a predominantly conductive signal. These interpretations are supported by Electron Microscopy and Atomic Force Microscopy. The proposed analysis allows improving the control of the concentration of NP deposited on surfaces systems with low coverage by impedance monitoring.