Structural, elastic, electronic, and optical properties of the tricycle-like phosphorene.

Phosphorene exhibits great potential applications in nanoelectronics due to its relatively large and direct band gap and good charge carrier mobility, and thus has attracted extensive attentions over the past few years. In this study, a novel hybrid phosphorene with a tricycle-like bulge is proposed using density functional theory calculations. Herein, structural stability, elastic, electronic, and optical properties have been addressed. It is found that all the hybrid phosphorenes are stable, and their cohesive energies are very close to that of black phosphorene monolayer. Due to the tricycle-like bulge, these hybrid layers are much softer than the black phosphorene. Their electronic band structures show that they are semiconductors with a robust indirect band gap, and their band gaps are strongly dependent on the sizes. Spatial charge distribution to the valence band maximum and the conduction band minimum is analyzed to explore the origin of the indirect band gap features. By calculating the complex dielectric function, optical properties have been discussed. Our results suggest that the hybrid phosphorenes with well structural stability, robust indirect band gaps, flexible property, and good optical absorption hold great promise for applications in the field of visible light harvesting and flexible nanoelectronic devices.

Robust indirect band gap and anisotropy of optical absorption in B-doped phosphorene.

A traditional doping technique plays an important role in the band structure engineering of two-dimensional nanostructures. Since electron interaction is changed by doping, the optical and electrochemical properties could also be significantly tuned. In this study, density functional theory calculations have been employed to explore the structural stability, and electronic and optical properties of B-doped phosphorene. The results show that all B-doped phosphorenes are stable with a relatively low binding energy. Of particular interest is that these B-doped systems exhibit an indirect band gap, which is distinct from the direct one of pure phosphorene. Despite the different concentrations and configurations of B dopants, such indirect band gaps are robust. The screened hybrid density functional HSE06 predicts that the band gap of B-doped phosphorene is slightly smaller than that of pure phosphorene. Spatial charge distributions at the valence band maximum (VBM) and the conduction band minimum (CBM) are analyzed to understand the features of an indirect band gap. By comparison with pure phosphorene, B-doped phosphorenes exhibit strong anisotropy and intensity of optical absorption. Moreover, B dopants could enhance the stability of Li adsorption on phosphorene with less sacrifice of the Li diffusion rate. Our results suggest that B-doping is an effective way of tuning the band gap, enhancing the intensity of optical absorption and improving the performances of Li adsorption, which could promote potential applications in novel optical devices and lithium-ion batteries.

Structural and electronic properties of ZnO/GaN heterostructured nanowires from first-principles study.

ZnO/GaN alloys have exceptional photocatalytic applications owing to their suitable band gaps corresponding to the range of visible light wavelength and thus have attracted extensive attention over the past few years. In this study, the structural stabilities and electronic properties of core/shell, biaxial, and super-lattice ZnO/GaN heterostructured nanowires have been investigated by means of first-principles calculations based on the density functional theory. The effects of the nanowire size, the GaN ratio, and strain have been explored. It is found that all studied heterostructured nanowires are less stable than pure ZnO nanowires, exhibiting larger sized wires with better structural stabilities and inversely proportional relationship between structural stability and the GaN ratio. Electronic band structures imply that all heterostructured nanowires are semiconductors with the band gaps strongly depending on the GaN ratios as well as mechanical strain. Particularly, for the biaxial and the super-lattice nanowires, their band gaps decrease firstly and then increase with the increasing GaN ratios. Electronic contributions to the valence band maximum (VBM) and the conduction band minimum (CBM) are discussed for exploiting the potential photocatalytic applications.

Strain-tunable electronic and optical properties of BC3 monolayer.

Two-dimensional layered nanostructures with unique electronic and optical properties may hold great potential in nanoelectronics and optoelectronics applications. In this work, structural stability, elastic, electronic, and optical properties of BC3 monolayers have been investigated using a first-principles study. The BC3 monolayer can be regarded as a series of hexagonal C rings with the connections of B atoms, which has been tested to be highly dynamically stable. The in-plane stiffness is 316.2 N cm-1, potentially rivalling graphene. A screened hybrid density functional HSE06 is used to calculate the electronic and optical properties. It is found that the BC3 monolayer is an indirect band gap semiconductor with a moderate gap energy of 1.839 eV. Spatial charge distribution to the valence band maximum and the conduction band minimum is analyzed to explore the origin of indirect band gap features. By calculating the complex dielectric function, optical properties considered as excitonic effects are discussed. Besides, the effects of various in-plane strains on electronic and optical properties are explored. Our results of good structural stability, moderate and tunable band gap, and strain-controllable optical properties suggest that the BC3 monolayer holds great promise in the applications of nanoelectronic and optoelectronic devices.