Observation of stacking faults in -phase InSe crystal

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 fi-InSe and other van der Waals crystals. However, the microstructure defects and deformability of e-InSe polytypes are still unclear. Performing scanning transmission electron microscopy (STEM), we reveal a type of stacking fault in e-InSe crystal that is associated with the Burgers vector +/- 1 3 [110] and usually appears after an even number of stackings of the Se-In-InSe 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 e-InSe is an excellent plastic material.