Theoretical Investigation on Self-passivation in Bare Zigzag Phosphorene Nanoribbons

Several bare zigzag phosphorene nanoribbons with odd number of atoms in the direction perpendicular to the extended line are investigated by using HSE06 density functional theory.These nanoribbons are as stable as those with even number of atoms.Primitive cells of the nanoribbons are metals,while edge self-passivation and distortion in the supercell structures cause metal-semiconductor transition.The band gaps of semiconducting nanoribbons are around 0.4 eV,which is enough for high on/off ratio in device operation.Compared to the conduction bands,the valence bands have smaller deformation potential constants and larger band width.Thus,the hole mobilities of the nanoribbons（10 cm^2·V^（-1）·s^（-1）） are one order higher than the electron mobilities.Bare zigzag phosphorene nanoribbons with odd number of atoms can also be candidates for small-size high-speed electronic devices.

Immunity of electronic and transport properties of phosphorene nanoribbons to edge defects

We present an extensive study of the electronic properties and carrier transport in phosphorene nanoribbons （PNRs） with edge defects by using rigorous atomistic quantum transport simulations. This study reports on the size- and defect-dependent scaling laws governing the transport gap, and the mean free path and carrier mobility in the PNRs of interest for future nanoelectronics applications. Our results indicate that PNRs with armchair edges （aPNRs） are more immune to defects than zig-zag PNRs （zPNRs）, while both PNR types exhibit superior immunity to defects relative to graphene nanoribbons （GNRs）. An investigation of the mean free path demonstrated that even in the case of a low defect density the transport in PNRs is diffusive, and the carrier mobility remains a meaningful transport parameter even in ultra-small PNRs. We found that the electron-hole mobility asymmetry （present in large-area phosphorene） is retained only in zPNRs for W 〉 4 nrn, while in other cases the asymmetry is smoothed out by edge defect scattering. Furthermore, we showed that aPNRs outperform both zPNRs and GNRs in terms of carrier mobility, and that PNRs generally offer a superior mobility-bandgap trade-off, relative to GNRs and monolayer MoS2. This work identifies PNRs as a promising material for the extremely scaled transistor channels in future posbsilicon electronic technology, and presents a persuasive argument for experimental work on nanostructured phosphorene.

Carbon-doping-induced negative differential resistance in armchair phosphorene nanoribbons

By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.

Even-odd-dependent optical transitions of zigzag monolayer black phosphorus nanoribbons

We analytically study the electronic structure and optical properties of zigzag-edged phosphorene nanoribbons(ZPNRs) using the tight-binding Hamiltonian and Kubo formula. By directly solving the discrete Schrodinger equation, we obtain the energy spectra and wavefunctions for N-ZPNR(where N is the number of transverse zigzag atomic chains) and classify the eigenstates according to the lattice symmetry. Then, we obtain the optical transition selection rule of ZPNRs on the basis of symmetry analysis and analytical expressions of optical transition matrix elements. Under incident light that is linearly polarized along the ribbon, we determine that the optical transition selection rule for N-ZPNR with even-or odd-N is qualitatively different. Specifically, for even-N ZPNRs, the inter-(intra-) band selection rule is ?n =odd(even) because the parity of the wavefunction corresponding to the n-th subband in the conduction(valence) band is(-1)~n[(-1)~((n+1))] owing to the presence of C(2x) symmetry. However, the optical transitions between any subbands are possible owing to the absence of C(2x) symmetry. Our results provide a further understanding on the electronic states and optical properties of ZPNRs, which are useful for explaining the optical experiment data on ZPNR samples.