Dongqing Zou

A first principle study on the spin transport properties in heterojunctions based on zigzag-edged graphene nanoribbons and graphitic carbon nitride nanoribbons

By using non-equilibrium Green’s functions (NEGF) and density functional theory (DFT), we investigate the spin-dependent electronic transport properties of two heterojunctions based on zigzag-edged graphene nanoribbons and graphitic carbon nitride nanoribbons. The only difference is the scattering region, i.e., one is zigzag-edged graphene nanoribbons (ZGNRs) and the other is graphitic carbon nitride (g-C3N4) nanoribbons. The I–V curves in the ferromagnetic and antiferromagnetic states for both devices are demonstrated. Our results show that the heterojunctions are promising multifunctional devices in molecular spintronics due to their nearly perfect spin-filtering efficiency (SFE) and high rectification ratio (RR). Spin negative differential resistance (SNDR) properties at low biases can also be found in the two devices. The mechanisms are proposed for these phenomena. The spin polarizations in the transmission spectra result in the nearly perfect SFE, the asymmetry in the structures gives rise to the high RR. Moreover, for the SNDR, the suppression of the transmission spectra is mainly caused by the localization in the total density of states.

Edge hydrogenation-induced spin-filtering and negative differential resistance effects in zigzag silicene nanoribbons with line defects

We investigate the effects of line defects (558-defect and 57-defect) and edge hydrogenation (mono-hydrogenation and di-hydrogenation) on magnetism and spin transport of zigzag silicene nanoribbons (ZSiNRs) by first-principles calculations. The line defects and edge hydrogenation are able to tune the edge and interedge spin polarization in the defective ZSiNRs. The ZSiNRs can be formed into antiferromagnetic (AFM)-metals, ferromagnetic (FM)-metals, AFM and FM semiconductors through modulating the line defects and edge hydrogenation. Moreover, the perfect spin-filtering effect (SFE) with 100% spin polarization and negative differential resistance (NDR) effect can be achieved by di-hydrogenation in our proposed devices. Our findings demonstrate that the ZSiNRs with diverse line defects and edge hydrogenation are promising materials for spintronic applications.

Vacancy-induced spin polarization in graphene and B–N nanoribbon heterojunctions

By using nonequilibrium Greens functions (NEGF) and density functional theory (DFT), we investigate the spin-separated electronic transport properties in heterojunctions constructed by zigzag graphene and boron nitride nanoribbons. The results show that the heterojunctions exhibit a strong spin polarization and ferromagnetic state when there is a vacant position in the boron nitride nanoribbons (BNNRs). The spin-filter effect can be significantly tuned and improved by the species of the nitrogen and boron vacancy and the location of the vacancy in the boron nitride nanoribbons with the spin-filter efficiency (SFE) up to nearly 100%. The spin negative differential resistance (SNDR) properties at low bias can also be found in the proposed molecular spin devices. Mechanisms for the results are suggested, and these findings open up new possibilities for developing nano-spintronic devices.

Design of boron vacancy enhanced spin filtering graphene/BN zigzag nanoribbon heterojunctions

The spin-polarized electronic transport properties of zigzag graphene nanoribbons (ZGNRs) and boron nitride nanoribbons (ZBNNRs) heterojunctions with a boron vacancy are investigated by using non-equilibrium Greens function and density functional theory, especially under an external electric field. The model we used in this paper is chosen from the last essay we researched, the I–V curves in the ferromagnetic states for (ZBNNR)5–(ZGNR)3–Bv devices are investigated, and the results show that with an external electric field, the heterojunctions are promising multifunctional devices in molecular spintronics due to their nearly perfect spin-filter effect, high rectification ratio and spin negative differential resistance properties at low biases. Mechanisms for such phenomena are proposed and these findings suggest a new opportunity for developing molecular spintronic devices.