Observation of stacking faults in ε-phase InSe crystal

Abstract

Defects in materials are one of the main causes of plastic deformation. Because of interlayer gliding and cross-layer dislocation slip, an exceptional plasticity has been demonstrated in β-InSe and other van der Waals crystals. However, the microstructure defects and deformability of ε-InSe polytypes are still unclear. Performing scanning transmission electron microscopy (STEM), we reveal a type of stacking fault in ε-InSe crystal that is associated with the Burgers vector ±13[11¯0] and usually appears after an even number of stackings of the Se-In-In-Se basic layer. Density functional theory calculations indicate that the stacking-fault energy of this type of defect may be as small as 8.8 mJ/m2. These results suggest that ε-InSe is an excellent plastic material.