Self-Assembled TaO_X/2H-TaS₂ as a van der Waals Platform of a Multilevel Memristor Circuit Integrated with a β-Ga₂O₃ Transistor

Two-dimensional (2D)-layered material tantalum disulfide (2H-TaS 2 ) is known to be a van der Waals conductor at room temperature. Here, 2D-layered TaS 2 has been partially oxidized by utraviolet-ozone (UV-O 3 ) annealing to form a 12-nm-thin TaO X on conducting TaS 2, so that the TaO X /2H-TaS 2 structure might be self-assembled. Utilizing the TaO X /2H-TaS 2 structure as a platform, each device of a β-Ga 2 O 3 channel MOSFET and a TaO X memristor has been successfully fabricated. An insulator structure of Pt/TaO X /2H-TaS 2 shows good a dielectric constant ( k ∼ 21) and strength (∼3 MV/cm) of achieved TaO X, which is enough to support a β-Ga 2 O 3 transistor channel. Based on the quality of TaO X and low trap density of the TaO X /β-Ga 2 O 3 interface, which is achieved via another UV-O 3 annealing, excellent device properties such as little hysteresis (<∼0.04 V), band-like transport, and a steep subthreshold swing of ∼85 mV/dec are achieved. With a Cu electrode on top of the TaO X /2H-TaS 2 structure, the TaO X acts as a memristor operating around ∼2 V for nonvolatile bipolar and unipolar mode memories. The functionalities of the TaO X /2H-TaS 2 platform become more distinguished finally when the Cu/TaO X /2H-TaS 2 memristor and β-Ga 2 O 3 MOSFET are integrated to form a resistive memory switching circuit. The circuit nicely demonstrates the multilevel memory functions.