Quantum Point Contact Dynamics and Conductance Quantization in MgO Memristors: Toward Multi‐Bit Storage

Magnesium oxide (MgO) is important for the memory devices primarily in magnetic tunnel junctions (MTJs) for magnetic random‐access memory (MRAM) devices. Here we report on the multibit memory characteristics, conductance quantization and shape of the nanogap at the nano‐constriction in an Ag/MgO/FTO memristor device. Quantum point contact (QPC) analysis reveals a wide nanogap at the nano‐constriction, supported by an energy‐barrier aspect ratio of t B / R ≈ 0.1947. The device exhibits stable bipolar switching with a window of ≈100, governed by space‐charge‐limited conduction in the high‐resistance state (HRS) and Ohmic transport in the low‐resistance state (LRS). During RESET, controlled filament rupture produces clear integer and half‐integer conductance quanta ( G 0 ), enabling robust 4‐bit (18 levels) quantized states. Pulse‐programming measurements further demonstrate ≈6.5‐bit (96 levels) current states. These results elucidate atomic‐scale filament evolution in MgO and highlight its promise for precision multilevel memory. The cycle‐to‐cycle variation, non‐linearity, and asymmetry ratio for LTP and LTD demonstrate the potential of the Ag/MgO/FTO memristor device for neuromorphic computing applications.