Collective amplification of nearby nanoparticles in the Coulomb blockade restricted charging of a single nanoparticle

Abstract

The characterization of charges in oxide supported metal nanoparticles (NP) is of high interest in research fields like heterogeneous catalysis and microelectronics. A general desire is to manipulate the charge of an oxide supported single NP and to characterize afterwards the charge and its interference with the insulating support but also with nearby NPs in the vicinity. By using noncontact AFM (nc-AFM) and Kelvin probe force microscopy (KPFM) in ultra-high vacuum and at room temperature we show that a ∼5 nm small AuNP can be directly charged with electrons by the AFM tip and that upon the charging, nearby AuNPs sensitively change their electrostatic potential with a large impact on the charge detection by nc-AFM and KPFM. The AuNPs are supported on a 40 nm thick insulating Al2O3 film, which is grown by atomic layer deposition on Si(001). Due to Coulomb blockades, the NP charging appears in the form of large and discrete peaks in detuning versus bias voltage curves. Finite element method calculations reveal that the large peaks can only be observed when the potentials of nearby insulated NPs get modified by the NP’s electron charge, according to the electrostatic induction principle. In view of the number of transferred electrons, we anticipate that after the charging, the electrons are transferred from the AuNP to the NP-Al2O3 interface or into Al2O3 subsurface regions directly underneath.

Quantifying nanoscale charge density features of contact-charged surfaces with an FEM/KPFM-hybrid approach

“…After and as a consequence of CE, we assume a thin layer of spatially varying surface charge σ (r q ) is present. By "thin," we mean confined to a region near the surface whose thickness is small compared to the tip-sample distance d. For materials similar to ours, this assumption is validated by the stability of charges on extremely thin substrates [20] and by the observance of dominant lateral diffusion [7].…”