Memristors have shown an extraordinary potential to emulate the plastic and dynamic electrical behaviors of biological synapses and have been already used to construct neuromorphic systems with in-memory computing and unsupervised learning capabilities; moreover, the small size and simple fabrication process of memristors make them ideal candidates for ultradense configurations. So far, the properties of memristive electronic synapses (i.e., potentiation/depression, relaxation, linearity) have been extensively analyzed by several groups. However, the dynamics of electroforming in memristive devices, which defines the position, size, shape, and chemical composition of the conductive nanofilaments across the device, has not been analyzed in depth. By applying ramped voltage stress (RVS), constant voltage stress (CVS), and pulsed voltage stress (PVS), we found that electroforming is highly affected by the biasing methods applied. We also found that the technique used to deposit the oxide, the chemical composition of the adjacent metal electrodes, and the polarity of the electrical stimuli applied have important effects on the dynamics of the electroforming process and in subsequent post-electroforming bipolar resistive switching. This work should be of interest to designers of memristive neuromorphic systems and could open the door for the implementation of new bioinspired functionalities into memristive neuromorphic systems.

Moisture and water penetration is one of the main phenomena altering the electrical characteristics and performance of resistive switching (RS) devices based on metal/insulator/metal nanojunctions. However, the effect of these phenomena in RS devices made of two dimensional (2D) materials has never been studied. In this paper it is shown that 2D materials based RS devices exposed to high relative humidity environments develop dielectric screening effects. The devices measured right after fabrication show a yield of 95% and bipolar RS characteristics, while after exposure to humid environments for two months the yield decreases to 65%. More than 30% of the devices show much lower currents than the fresh counterparts, and at high voltages they exhibit clear dielectric screening effects. This behavior is even more accentuated in RS devices that require the transfer of the 2D material, and we observe that a baking step at 120°C for 5 min can mitigate this effect.

Thanks to their excellent thermal and optical properties, graphene oxide quantum dots (GOQD) have been extensively explored for several applications, such as composite material, optoelectronic devices, solar cells, and fluorescence materials, among others. Consequently, GOQDs are commercially available suspended in a solution. However, the density, size, and crystallinity of commercially available GOQDs can differ a lot from one manufacturer to another, which rarely provide exhaustive information about them. Furthermore, a recent report has questioned the quality of graphene‐based materials produced by liquid phase exfoliation. Here a statistical analysis of the quality of commercially available GOQDs, using transmission electron microscope (TEM), is presented. This technique enables to observe the internal structure, thickness, lattice structure, orientation, and local defects of the samples at atomic scale. High resolution TEM images reveal that the thickness of the GOQDs is not homogenous from center to edges within one single domain. The edges show hexagonal lattice (monolayer) while the central location shows to be rhomboidal structure (multilayer). This work provides clear statistical information about the quality of the commercially available GOQDs.