In-situ transmission electron microscopy of conductive filaments in NiO resistance random access memory and its analysis

Abstract

We used thermal oxidization at various temperatures to prepare NiO/Pr-Ir for use in resistance random access memory (ReRAM) samples. In-situ transmission electron microscopy (TEM) was used to investigate the forming process of these ReRAM samples, where a needle-shaped top electrode of Pt-Ir was attached to the NiO/Pt-Ir ReRAM layer. The forming voltage initializing the NiO layer increased at an oxidization temperature of between 200 and 400 C. In this process, conductive bridges, which are thought to be conductive filaments of a ReRAM, appeared, and their sizes showed a correlation with the injection power. It was as small as about 300 nm 2 when the injection power was 10 À6 W. Energy dispersive X-ray spectroscopy was used to analyze the bridge, and it was experimentally confirmed that the oxygen content of the bridge was lower than that of the initial NiO layer. However, these bridges in the low resistance state did not show further ReRAM switching to the high resistance state inside of a TEM instrument. To check the reason of this result, we investigated samples outside of the TEM instrument, which had similar geometry to that of TEM specimens. They showed the ReRAM switching in air ambient but not in vacuum. Combining these results inside and outside of the TEM instrument, it can be concluded that the existence of oxygen around the conductive filament plays an important role. This supports the filament redox model on the ReRAM operation. V C 2013 American Institute of Physics.

Probing electrochemistry at the nanoscale: in situ TEM and STM characterizations of conducting filaments in memristive devices

“…The CF contained less oxygen than the bulk of the oxide (Fig. 15c-d) [47], and its diameter decreased by reducing the current. However, the subsequent RESET was not achieved because the oxygen liberated during electroforming escaped into the vacuum.…”

Microstructural transitions in resistive random access memory composed of molybdenum oxide with copper during switching cycles

“…In addition to perovskite-type ReRAMs [37][38][39] and devices based on binary oxides, [40][41][42][43][44][45][46] many reports on CBRAMs have appeared in recent years. [47][48][49][50][51][52][53] In one example, the dynamic growth and rupture of a Cu CF was confirmed during a switching cycle.…”

Filament formation and erasure in molybdenum oxide during resistive switching cycles

“…To investigate the switching operation in real space, in-situ transmission electron microscopy (TEM) [25][26][27][28][29][30] has been applied to ReRAMs of various solid electrolytes. [31][32][33][34] Fujii et al 31,32 dynamically observed the growth and rupture of a conductive filament made of Cu in the Cu-Ge-S layer deposited on a needle-shaped Pt-Ir electrode.…”