Nanoimaging of Organic Charge Retention Effects: Implications for Nonvolatile Memory, Neuromorphic Computing, and High Dielectric Breakdown Devices

Abstract

A large variety of organic and molecular materials have been found to exhibit charge memory effects. However, the mechanism of charge storage is not well understood, which is a key bottleneck for the development of stable and scalable organic memory devices. Here study the charge retention mechanism of organic molecules using a model system, a grafted organic monolayer (GOM) on a silicon substrate. Au nanoparticles (NPs) are used as non-destructive nano-electrodes with controlled contact area. Using a scanning probe, we manipulate and image the charge state of the system with nanoscale resolution. We show, via control experiments, that amine functional groups in the GOM molecules play a vital role in charge retention. Density functional simulations show a possible route of molecular distortion that leads to metastable charge states. Our findings shed light to the mechanism of polaronic effects and their role in facilitating charge storage in nanoscale organic systems.

Multiscale Characterization of the Influence of the Organic–Inorganic Interface on the Dielectric Breakdown of Nanocomposites

“…A second KPFM measurement is carried out afterward in order to map the resulting trapped charges with nanoscale resolution following an existing procedure further detailed in the Methods. 28 From these charge-injection measurement results, we observe noticeable charge retention capabilities of the two molecules with an amine-terminating group. The application of both a negative (−1.5 V) or positive (+1.5 V) potential while contacting the NP results respectively in an increase (Figure 1F,G) and decrease (Figure 1I−J) of the measured CPD.…”

“…These observations are in line with our previous findings where a grafted monolayer on a Si surface terminated by -CONH(CH 2 ) 2 NH 2 interfacing with the Au NPs exhibited charge retention, while the -(CH 2 ) 3 COOH terminated grafted monolayer interfacing with Au NPs did not. 28 Here we observe that solely the presence of an amine group at the interface with the Au NP is sufficient to allow for charge retention, thus questioning the mechanism previously proposed.…”

“…Next, we use the AFM tip to directly contact the gold NP and inject charges locally into the junction. A second KPFM measurement is carried out afterward in order to map the resulting trapped charges with nanoscale resolution following an existing procedure further detailed in the Methods …”

“…Scanning probe techniques allow for the investigation of interfaces at the nanoscale. ,, The charge state in grafted organic monolayers on a silicon substrate, with Au NPs deposited on top has been studied using such techniques. , Stable charge retention in the Au NPs, attributed to polaron effects at the amine functional group, was observed when the organic monolayer was terminated by -CONH­(CH 2 ) 2 NH 2 . This charge retention at the organic–inorganic interface is expected to affect the dielectric breakdown behavior of these molecular junctions.…”

Enhancing Technological Applications through Density Functional Theory Modeling of Nanomaterials

“…Quantum effects are also important in diverse phenomena related to field emission, charge transport, or retention. In this context, the interfacial properties (i.e., Schottky barriers) of InSe−M (M = Ag, Sc, Cu Au, Pd, and Pt) contacts, 23 the electronic conductance of phenyl-chain-based molecular junctions, 24 the electron emission performance of CsPbI 3 − reduced graphene oxide (rGO) composite, 25 and the chargeretention properties of Au deposited on a Si/organic monolayer 26 were reported.…”