Transparent-conductive-oxide (TCO) buffer layer effect on the resistive switching process in metal/TiO2/TCO/metal assemblies

Abstract

The effect of a transparent conductive oxide (TCO) buffer layer on the insulator matrix and on the resistive switching process in the metal/TiO _2 /TCO/metal assembly was studied depending on the material of the TCO (ITO-(In _2 O _3 ) _0.9 (SnO _2 ) _0.1 or SnO _2 or ZnO). For the first time electro-physical studies and near edge x-ray absorption fine structure (NEXAFS) studies were carried out jointly and at the same point of the sample, providing direct experimental evidence that the switching process strongly influences the lowest unoccupied bands and the local atomic structure of the TiO _2 layers. It was established that a TCO layer in a metal/TiO _2 /TCO/metal assembly is an additional source of oxygen vacancies for the TiO _2 film. The R _L ( R _H ) states are achieved presumably with the formation (rupture) of the electrically conductive path of oxygen vacancies. Inserting an Al _2 O _3 thin layer between the TiO _2 and TCO layers to some extent restricts the processes of migration of the oxygen ions and vacancies, and does not allow the anti-clockwise bipolar resistive switching in a Au/TiO _2 /Al _2 O _3 /ITO/Au assembly. The greatest value of the ratio R _H / R _L is observed for the assembly with a SnO _2 buffer layer that will provide the maximum set of intermediate states (recording analog data) and increase the density of information recording in this case.

Keywords

• resistive switching
• transparent-conductive-oxide
• NEXAFS
• I–V characteristics
• oxygen vacancies
• buffer layer