Atomistic Mechanisms of the Crystallographic Orientation‐Dependent Cu_1.8S 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, Cu_2-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 Cu_1.8S 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 Cu_2-xS as a versatile material for neuromorphic computing.