Atomistic Mechanisms of the Crystallographic Orientation‐Dependent Cu1.8S Conductive Channel Formation in Cu2S‐Based Memristors

Achieving multiple types of resistive switching in a single material with controlled ionic motion is a key challenge in neuromorphic computing, traditionally addressed by combining materials with distinct switching behaviors. Here, Cu2‐xS is identified as a promising candidate to overcome this limitation due to its hierarchical phase transitions. Using in situ biasing experiments, reversible and non‐reversible phase transitions (and resistive switching) are demonstrated in γ‐Cu2S by controlling the compliance current. The formation of parallel high‐digenite Cu1.8S channels, orientated along the γ‐Cu2S [201] crystallographic direction, drives the nonvolatile resistive switching. These channels emerge via an intermediate δ‐Cu2S phase and are stabilized at room temperature by residual strains, alongside β‐Cu2S phase. The work clarifies the complex, electrically triggered phase transformations in γ‐Cu2S, and highlights the potential of Cu2‐xS as a versatile material for neuromorphic computing.