Tuning the electronic transport anisotropy in borophene via oxidation strategy

Monolayer borophene, a novel kind of two-dimensional(2D) crystal, has been receiving intensive attention owing to its atomic thickness and metallic characteristics. Rational tuning the anisotropic electronic transport properties is essential to the application of monolayer borophene in electronic and optoelectronic devices. Herein, we developed an oxidation strategy to tune the anisotropic transport properties of borophene by changing O-defect coverage, using density functional theory combined with the nonequilibrium Green's function formalism. It was found that for monolayer borophene, the preferable current flowing direction between armchair and zigzag could be reversed by modulating the surface O-defect coverage between 0 and 100%. The tunable anisotropic transport properties of oxidized borophene could be attributed to the interplay among several factors, including the surface charge transfer between O-defects and borophene layer, the scattering effects related to the coverage and orientation of O-B-O interfaces, and the additional transport channels through O-defects. Our work unveils the great potential of oxidization strategy in tuning the anisotropic electronic transport properties of monolayer borophene and is of significance to its application in high-performance electronic and optoelectronic nanodevices.

Two-dimensional phosphorene/C_3N p-n heterostructure: Effect of contact type on electronic and optical properties

p-n heterostructure(HTS) is a fundamental component for high-performance electronic and optoelectronic device. Vertical stacking through van der Waals(vdW) force is emerging as a feasible technique to construct p-n HTS. Herein, we designed a novel kind of direct-bandgap C_3N monolayer, via adjusting the arrangement of C and N atoms in C_3N hexagonal cell. On the basis of the density functional theory combined with the non-equilibrium Green's function method, we built two-dimensional vdW-contact phosphorene(BP)/C_3N p-n HTS, and analyzed its electronic and optical properties in comparison with the inplanejointed ones. The strong charge transfer between BP and C_3N segments results in a wide bandgap of 0.48 eV for joint-contact type BP/C_3N HTS, whereas the effective interlayer coupling in vdW-contact type leads to an improved light adsorption as compared to the isolated C_3N monolayer. By fabricating dual-gated BP/C_3N HTS field-effect transistors(FETs), the dynamic transport behaviors demonstrated that the band bending under a lower threshold voltage makes band-to-band tunneling possible for vdW-contact type. Our work suggests that vdW-contact type is superior to joint-contact type in constructing p-n HTS for high-performance electronic and optoelectronic devices.