Electrical conduction in nanogranular cluster-assembled metallic films

Abstract

A film fabricated by the assembling of nanoparticles that retain, at least partially, their individuality is expected to show substantially different structural and functional properties compared to the case where atoms or molecules are used as building blocks. Although films assembled with metallic clusters or nanoparticles have been predicted to have unusual functional properties, it has been tacitly assumed that cluster-assembled metallic films have the same conduction behavior observed for polycrystalline metallic thin films grown from atoms. Unexpectedly, in the last decade, several studies showed that nanogranular metallic films show a non-linear electric behavior, substantially different from their polycrystalline counterparts. Here we review and discuss the electrical transport properties of cluster-assembled films. Our aim is to provide a background and a common language for the systematic investigation and exploitation of nanogranular metallic thin films where the extremely high density of defects and grain boundaries causes the departure from ohmic behavior. We will focus on the non-linear electrical conduction and resistive switching relevant for neuromorphic applications.

Sparse CNT networks with implanted AgAu nanoparticles: A novel memristor with short-term memory bordering between diffusive and bipolar switching

“…The deposition time for the nanoparticles has been set to stay below the percolation point [ 37 ]. The deposition time for the percolation point has been determined by performing electrical measurements in-operando during deposition.…”

Modelling charge transport in gold nanogranular films

“…All the gold clusters were first thermalized at 300 K for 150 ps. The size population of the clusters was constructed with 70% of the clusters of diameters 8.8 nm and 30% of diameters 1.3 nm, thus reproducing the experimental sizedistribution [13].…”

“…In particular, 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 near-to-percolation 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]. In particular, for this latter situation a well-established explanation of the underlying physical mechanisms is still missing.…”

“…Atomistic simulations may help to get insights on the microscopic mechanisms responsible for such phenomena. Correctly estimating the electrical conductivity becomes therefore crucial [13,14]. To this end, we developed an atomically informed mesoscopic model which provides accurate conductivity estimates for systems composed by interconnected gold nanoclusters.…”

Analytical model of the acoustic response of nanogranular films adhering on a substrate

“…Nanogranular ultrathin films are at the forefront of a wide range of technological applications [1] ranging from nanomedicine [2], sensing [3][4][5] to electronics [6][7][8][9][10][11][12]. Accessing their mechanical properties, both within the film's bulk and at the interface region in contact with the supporting substrate, is among the most urgent issues in view of any device development.…”