Scalable Memdiodes Exhibiting Rectification and Hysteresis for Neuromorphic Computing

Abstract

Metal-Nb2O5−x-metal memdiodes exhibiting rectification, hysteresis, and capacitance are demonstrated for applications in neuromorphic circuitry. These devices do not require any post-fabrication treatments such as filament creation by electroforming that would impede circuit scalability. Instead these devices operate due to Poole-Frenkel defect controlled transport where the high defect density is inherent to the Nb2O5−x deposition rather than post-fabrication treatments. Temperature dependent measurements reveal that the dominant trap energy is 0.22 eV suggesting it results from the oxygen deficiencies in the amorphous Nb2O5−x. Rectification occurs due to a transition from thermionic emission to tunneling current and is present even in thick devices (>100 nm) due to charge trapping which controls the tunneling distance. The turn-on voltage is linearly proportional to the Schottky barrier height and, in contrast to traditional metal-insulator-metal diodes, is logarithmically proportional to the device thickness. Hysteresis in the I–V curve occurs due to the current limited filling of traps.

Photopatternable solid electrolyte for integrable organic electrochemical transistors: operation and hysteresis

“…However, it has been shown that if controllable, hysteresis can be harnessed in neuromorphic devices as a short- or long-term memory effect. 8,10,38 In this regard, we examine the hysteresis in the transfer curves of our PEDOT:PSS-based solid OECTs and show how its magnitude can be controlled.…”

Structural Phase Transitions of NbO2: Bulk versus Surface

“…These observations are explained in Figure b, which shows the XPS spectra of the Nb 3d core region during the annealing processes. There are two niobium oxidation regions that are distinguished by references (vertical lines) of previously investigated amorphous Nb 2 O 5 (Nb 5+ ) and NbO 2 (Nb 4+ ) thin films. The Nb 5+ oxidation state is assigned to the immediate surface, while the Nb 4+ oxidation state is attributed to the subsurface and bulk, agreeing with vanadium oxidation states in VO 2 thin films .…”

Diffuson-driven ultralow thermal conductivity in amorphous Nb2O5 thin films

“…X-ray photoelectron spectroscopy (XPS) was used to determine the ratio of Nb and O atoms in the films. 27 The Nb:O ratios of films with different growth powers are shown in Table 1.…”