Local chemical state change in Co–O resistance random access memory

Abstract

Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Memory Retention Characteristics of Data Storage Area Written in Transition Metal Oxide Films by Using Atomic Force Microscope.

“…Physical and chemical analyses of the filament by conventional analytical methods have therefore been hindered for a long time. Against this background, overcoming the above-mentioned difficulties by using conductive atomic force microscope (C-AFM) was reported to be possible [3,[5][6][7]. That is, by directly contacting transition metal oxide films with an AFM-tip and scanning the tip under application of dc bias voltage, a large area with an arbitrary resistance can be formed without a top electrode being deposited.…”

“…However, the conductive filamentary paths, termed "filaments", are sandwiched between a top and bottom electrode. Moreover, it was reported that the diameter of the filaments is very small; some groups even reported the diameter to be less than 50 nm [3][4][5]. Physical and chemical analyses of the filament by conventional analytical methods have therefore been hindered for a long time.…”

Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2heterointerface probed by anin situhard x-ray photoemission and soft x-ray absorption spectroscopies

“…Various attempts have been carried out using transmission electron microscopy [9, 10], atomic force microscopy [11] and other microscopy techniques to find experimental evidence that such switching behavior is caused by ion migration even at room temperature, through this ion transport is extremely slow at ambient temperatures. Now, atomistic pictures of the conducting path formation are becoming evident, supported by indirect observations for some devices to date, while most of the proposed models still include a certain amount of speculation.…”

Bias application hard x-ray photoelectron spectroscopy study of forming process of Cu/HfO2/Pt resistive random access memory structure

“…One is oxygen vacancy nucleation at a metal/oxide interface. [8][9][10] Yang et al observed indirectly that oxygen vacancies are created and drift towards the cathode, forming localized conducting channels at Pt/TiO 2 /Pt cross-point junctions. 8 We observed the Pt electrode oxidization and oxygen vacancy formation at the interface of the Pt/HfO 2 /Pt system directly using hard x-ray photoelectron spectroscopy (HX-PES) under bias operation.…”