Semimetal Bi/MoS2 Memristor Exhibiting Ultrahigh Switching Ratio and Mechanistic Insights Into Transport via Low-Temperature Characterization

The semimetal Bi top electrode (TE) provides a low Schottky barrier and reduced contact resistance, enabling an ultrahigh on/off ratio exceeding 106 , endurance up to 10^3 cycles, and retention longer than 10^4 s. The devices show highly uniform bipolar switching with forming-free operation and tight cycle-to-cycle and device-to-device distributions.

Time-dependent dielectric breakdown (TDDB) suggests improved resistance to constant-stress degradation in Bi-based devices compared with Al-capped counterparts, which is attributed to suppressed sulfur-vacancy-assisted leakage. Temperature-dependent I – V characteristics down to 20 K reveal distinct conduction regimes: direct tunneling and Poole–Frenkel emission in the high-resistance state (HRS), and a Schottky-to-Ohmic transition in the low-resistance state (LRS).