▎ 摘　　要

Graphene is an atomically thin two-dimensional material which is well suited for kirigami-like cutting. We constructed a class of four-zigzag-edged parallelogram-shaped cutting graphenes as scattering region, forming an angle of 60 with electrodes. Based on the first-principles transport calculations, we have illustrated that this system has perfect spin filtering effect, which arises from hybrid spin states in occupied orbitals and bias-induced spin reversal in one of zigzag edges connecting to the electrodes. The spin filtering effect is reinforced with increasing the length of scattering region below a critical value, beyond which the effect may disappear. Fortunately, curling the cutting graphenes into threedimensional helical structures can maintain the desirable transport properties in a much larger critical size. The results suggest that monolayer graphene can be tailored into perfect flexible spin filters, which may lead to important applications in spintronics and flexible electronics. (C) 2017 Elsevier Ltd. All rights reserved.