Orientation-dependent large plasticity of single-crystalline gallium selenide

Unlike metals and alloys with high ductility, inorganic semiconductors are mostly ceramics with brittle nature due to covalent/ionic bonding. Recent studies have shown that some layered/van der Waals semiconductors could exhibit substantial room-temperature ductility, despite the fact that the underlying mechanisms remain to be understood. Here, we report that the van der Waals semiconductor gallium(II) selenide (GaSe) can have crystal-orientation-dependent large plasticity at room temperature. Through in situ tensile and compressive experiments inside electron microscopes, we demonstrate that microfabricated GaSe can have substantial ductility loaded along and slanted with the intralayer direction while showing predominantly elastic deformation perpendicular to the intralayer direction until brittle fracture. We further reveal that, despite the interlayer gliding as the main mechanism, cross-layer slips induced by buckling associated with stacking faults also contribute to the plasticity. This study offers insights to understand the ductility and plasticity of van der Waals semiconductors and shows promising flexible/deformable electronics and energy-device applications.