Microscopic origins of hysteresis and conduction mechanisms of defective MoS 2 /Au(111)-based devices

We present a first-principles investigation of vertical Au(111)/monolayer MoS 2 /Au(111) heterostructures that links atomic-scale structural evolution, defect energetics, and bias-dependent transport barriers to memristive switching behavior. Three distinct and concurrent hysteresis mechanisms are revealed: (i) sliding-induced hysteresis of the MoS 2 layer, which also occurs in the absence of defects, (ii) defect-driven hysteresis associated with adatom motion and registry changes between MoS 2 and Au, and (iii) electronic-based hysteresis arising from reversible transitions between different conduction mechanisms (electron-barrier limited, defect mediated, Ohmic) due to band bending. Our calculations reveal how these mechanisms of hysteresis act through a nonlinear modulation of the effective electron injection barriers at the metal-semiconductor interface. This barrier modulation directly controls charge injection, trap occupation, and the activation of different conduction regimes. To connect to transport characteristics, we employ a non-equilibrium Green's function approach within an effective-mass model using the bias-dependent barrier profiles extracted from first-principles calculations and find a switching ratio of two orders of magnitude, consistent with measurements. The resulting framework provides a unified microscopic description of hysteresis in vertical memristors based on defects in monolayer materials.