Two terminal metal-oxide-metal (MOM) devices based on niobium oxides (NbO_x) have drawn much attention due to their ability to show reliable resistive switching for next generation memory and brain-inspired computing applications. NbO_x based MOM devices show two distinct responses: non-volatile memory switching that creates a semipermanent resistance change and volatile threshold switching that creates a temporary change. These resistance changes are commonly mediated by filamentary conduction, either in the form of a semi-permanent filament created by compositional changes in the oxide or as a transient filament created by inhomogeneous current or field distributions (e.g. current bifurcation). Knowledge about the structure, composition and spatial distribution of filaments is essential for a full understanding of filamentary resistive-switching and for effective modelling and optimisation of associated devices. Additionally, the dominant switching mode in NbO_x is controlled by the composition, choice of electrode metals and device geometry. Thus, a proper understanding of these factors is important for achieving reliable resistive switching with desired characteristics. In this talk, I will focus on two aspects of resistive switching: filament detection and the effect of electrodes.

The first part of my talk will focus on a recently developed simple technique to detect conductive filaments in MOM cross-point devices based on decolourisation of a thin photoresist layer. The usefulness of this method will be discussed by filament detection in NbO_x system and a statistical distribution of the location of filament formation will be presented as a function of device area. The later part of the talk will be focussed on the effect of reactive electrodes on the resistive switching properties of NbO_x based MOM devices