Although ferroelectric materials show great promise for nonvolatile memory applications, conventional bulk ferroelectrics suffer from performance degradation as device dimensions are reduced to the nanoscale, owing to increased polarization-reversal cycles and sensitivity to defects. Interestingly, two-dimensional sliding ferroelectrics, featuring atomic-scale thickness and a unique interlayer-sliding polarization switching mechanism, offer unique opportunities for device miniaturization. However, whether unavoidable common local point vacancy defects and adsorption of ambient gas molecules impact their performance as in traditional bulk ferroelectrics remain unclear. Herein, we conduct a systematic investigation into the effects of local point vacancy defects and adsorption of ambient gas molecules (${\mathrm{O}}_2, {\mathrm{CO}}_2, {\mathrm{H}}_2\mathrm{O}$, and ${\mathrm{H}}_2$) on representative two-dimensional sliding ferroelectric materials, including h-BN, 3R-${\mathrm{MoS}}_2$, γ-InSe, and ${\mathrm{WGe}}_2{\mathrm{N}}_4$. We find that the influence of local symmetry breaking on polarization fluctuations is minimal (within $\pm 10\%$). Specifically, the polarization switching in sliding ferroelectrics occurs through the relative sliding of atomic layers—without breaking or reconstructing intralayer chemical bonds—which contrasts with conventional bulk ferroelectrics that rely on intralayer ionic displacement. Moreover, even under local symmetry breaking, the switching energy barrier remains low (on the order of meV per atom). This work paves the way for designing next-generation miniaturized ferroelectric devices with superior reliability and defect resilience.

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• Defects
• Electric polarization
• Ferroelectricity
• 2-dimensional systems
• Density functional calculations