Theoretical study of the line defect in x3-borophene: structures, electronic properties, direct-current and alternating-current transport properties

Two-dimensional material x3-borophene is a stable borophene allotrope and has been synthesized in experiment. Combining density functional theory with non-equilibrium Green's function method, in the present study we theoretically investigated the structures, stabilities, electronic properties, and the direct-current (DC) and alternating-current (AC) transport properties of its line defects. The obtained results suggest that along the zigzag direction there exist some special line defects that can enhance the stability of x3-borophene and the six -coordination B atoms play a key role for the enhanced stability. The line defects may change the atomic orbital components of the Dirac cone of x3-borophene and have profound influences on the electronic properties. For the DC transport, under high bias voltages along a given transport direction the line defects may lead to constant current phenomena. For the AC transport, under different frequency ranges the line defects have different AC responses with respect to the external time-dependent field, exhibiting complicated AC transport behaviors. Furthermore, for the low-frequency range, the equivalent circuits of x3-borophene and its line defects were suggested, which will be beneficial for designing borophene-based functional nanodevices.