Abstract
Cluster-assembled metallic films show interesting electrical properties, both in the near-to-percolation regime, when deposited clusters do not form a complete layer yet, and when the film thickness is well above the electrical percolation threshold. Correctly estimating their electrical conductivity is crucial, but, particularly for the latter regime, standard theoretical tools are not quite adequate. We therefore developed a procedure based on an atomically informed mesoscopic model in which ab-initio estimates of electronic transport at the nanoscale are used to reconstruct the conductivity of nanogranular gold films generated by molecular dynamics. An equivalent resistor network is developed, appropriately accounting for ballistic transport. The method is shown to correctly capture the non-monotonic behavior of the conductivity as a function of the film thickness, namely a signature feature of nanogranular films.
Highlights
Cluster-assembled metallic films may play an important role in the development of emerging technologies. They show a resistive switching behavior [1] that can be exploited in the fabrication of electrical devices able to process and store data in the same physical unit [2,3,4], as requested by the neuromorphic computing paradigm [5,6]. Such behavior emerges in the nearpercolation regime [7,8,9], when deposited clusters do not form a complete layer of the film yet, as well as when the film thickness is well above the electrical percolation threshold [10,11,12,13]
The hierarchy of molecular dynamics (MD), nonequilibrium Green’s function (NEGF)-density functional theory (DFT), and equivalent resistor network (ERN) models allows to compute the evolution of the film electrical resistance as gold clusters are deposited on the substrate
The determination of the film thickness, t, is performed following the definition used to plot the results of the experiments in Ref. [10]: we count the number of cells containing Au atoms in the ERN grid, Nc
Summary
Cluster-assembled metallic (or, “nanogranular”) films may play an important role in the development of emerging technologies. We model the metallic component as a collection of amorphous regions mixed with pristine crystalline ones and assume that electronic transport within each region and between regions of the same phase (whose length scale is typically just of a few nanometers) is mainly ballistic, while between regions of different phase the transport is diffusive Such a picture is encoded in an ERN by requiring that resistors contribute to the overall resistance either ballistically or diffusively, whether they connect regions with the same or different phases, respectively. We use density functional theory (DFT) combined with nonequilibrium Green’s function (NEGF) techniques (i) to study ballistic transport in structures mimicking the inhomogeneities found in the nanogranular film and (ii) to determine appropriate values of resistance for the ERN Provided with such an input, the ERN can be used to get an estimate of the conductance of the entire simulated system. V we present the results provided by our electrical model and compare them to a set of experimental results
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
