Combinatorial Screening of Anodically Formed Ti–Hf Oxides for Interfacial Memristive Switching

This work presents an investigation of the memristive properties of anodically formed Ti–Hf mixed oxide fabricated from a simultaneously sputtered Ti–Hf combinatorial alloy library spanning 15–90 at.% Hf. The specimens exhibit electroforming-free, volatile, analog switching with strong self-rectification and compositional tunability. Electrical characterization revealed a systematic increase in the SET voltages and a corresponding decrease in the RESET voltages with increasing Hf content. Three distinct compositional regions were identified: Zone 1 (15–30 at.% Hf) showing excellent endurance (≥106 cycles) and moderate ON/OFF ratios, Zone 2 (30–50 at.% Hf) with high multilevel switching capabilities but poor endurance and stability, and Zone 3 (50–90 at.% Hf) with enhanced ON/OFF ratios and stable switching thresholds. Current conduction analysis confirmed Schottky emission in both high and low resistive states, in agreement with the interfacial switching characteristics revealed by the electrical performance of the devices. These results, supported by detailed structural and chemical characterization via high-resolution transmission electron microscopy techniques and X-ray photoelectron spectroscopy, demonstrate the prominent potential of using anodic Ti–Hf oxides for stable, tunable, and filament-free memristive devices with applications in analog switching for neuromorphic computing.