Properties of innovative resistive memories studied by X-ray and UV photoemission

Pt/NiO‐based devices are promising candidates for the next generation of resistive random access memories (RRAMs). X‐ray (XPS) and ultraviolet (UPS) photoemission are performed to investigate the chemical and electronic properties of this stack. After resistive switching of the nickel oxide, the as‐deposited and switched areas are compared in situ. The surface of the conductive area is characterised by a higher oxygen content as well as an enhancement of Ni3+ oxidation state, which can be related to defects such as Ni vacancies. The results are compatible with a bias‐induced diffusion of O2− towards the anode, and a migration of Ni2+ towards the cathode. The NiO electron affinity is estimated to be 1.6 eV by UPS in the OFF state, leading to a Pt/NiO barrier height of 3.6 eV. Copyright © 2010 John Wiley & Sons, Ltd.