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

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.