Abstract Niobium oxide (NbO x ) memristors have shown significant promise for neuromorphic computing by emulating neuronal behavior. However, the complex phase compositions arising from niobium’s multiple valence states critically influence device performance. Here, we demonstrate precise control over NbO x thin film phases (including NbO, NbO 2 , Nb 2 O 5 , and mixed phases) by modulating oxygen concentration and temperature during magnetron sputtering deposition. A resulting phase preparation diagram is corroborated by density functional theory (DFT) calculations of formation energies. Comprehensive optical and electrical characterization reveals how NbO x phase composition governs intrinsic properties—optical bandgap, resistive switching, and negative differential resistance characteristics. Moreover, in Pt/NbO x /Pt devices, we establish that the electric-field-driven conduction is governed by oxygen vacancy concentration and mobility. This mechanism is visualized directly via Kelvin probe force microscopy (KPFM), which maps the potential profiles and charge density distribution linked to vacancy migration. These findings offer crucial insights and present fundamental design principles for tailoring NbO x memristors, essential for the advancement of future-generation neuromorphic hardware.
Lu et al. (Tue,) studied this question.