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This paper investigates the complex deformation behavior of layered GeSe, revealing that its plastic response is highly dependent on crystallographic orientation, sample size, and loading conditions, with macroscopic compression enabling significant strain while micropillar compression leads to brittle fracture. The study highlights that a single experimental approach is insufficient to characterize plasticity, as different testing methods (macroscopic compression, bending, conventional vs. eccentric micropillar compression) elicit contrasting behaviors due to coupled effects of bonding, interlayer interactions, defects, and stress constraints. The findings underscore the critical need for more rigorous and unified criteria, combining multiple testing modalities and characterization techniques, to reliably identify plastic inorganic semiconductors for applications in flexible electronics.
Plasticity in layered semiconductors is an illusion of experimental design, with brittle fracture dominating under common micro-scale tests but significant plastic deformation achievable via controlled eccentric loading.
The identification of plastic inorganic semiconductors becomes challenging when their mechanical responses depend on crystallographic orientation, sample size, and loading conditions. Using layered GeSe as a model system, we examine its deformation behavior through macroscopic compression, bending, conventional micropillar compression, and eccentric micropillar compression. Under macroscopic compression perpendicular to the layers, GeSe sustains approximately 23% strain without fracture, whereas bending along the c-axis armchair direction produces brittle cleavage fracture. Conventional micropillar compression results in brittle fragmentation, while eccentric loading introduces a shear component that activates pronounced interlayer sliding and accommodates deformation. These contrasting responses reflect the coupled effects of bonding topology, interlayer van der Waals interactions, defect density, stress constraints, and strain path on the competition between sliding and fracture. The results highlight the limitations of identifying plasticity from a single direction, scale, or test and support a systematic evaluation framework combining multiple directions, length scales, loading modes, and characterization techniques. More rigorous and unified criteria are needed to guide reliable materials selection for flexible electronics and devices integrated on curved surfaces.