arXiv subjects

Haifang Cai

Publications and source records attributed to Haifang Cai.

3 recordsLinked to original sources

arXiv2024

A 2D T-carbon 2-(111) structure with tunable electric and optical properties via chemical decorations: a first-principles investigation

We proposed a new two-dimensional carbon material named 2-(111) planar T-carbon, which is obtained by slicing bulk T-carbon along its (111) crystallographic direction. 2-(111) planar T-carbon's optical and electrical properties can be engineered via surface decoration. Comparing the DFT phonon spectra of pristine and five decorated 2-(111) planar T-carbon obtained by first-principles calculations, we conclude that surface decoration presents a promising, effective, and feasible strategy to improve the structural stability of 2-(111) planar T-carbon. The calculated band structures and electronic properties show direct electronic band gap values between 0.17 eV (-O= decorated) and 2.21 eV (Hydrogenated). Chemical decoration also promises blue or red energy shifts in its optical properties.

cond-mat.mtrl-sci↗

arXiv2021

Direct observation of layer-stacking and oriented wrinkles in multilayer hexagonal boron nitride

Hexagonal boron nitride (h-BN) has long been recognized as an ideal substrate for electronic devices due to its dangling-bond-free surface, insulating nature and thermal/chemical stability. Therefore, to analyse the lattice structure and orientation of h-BN crystals becomes important. Here, the stacking order and wrinkles of h-BN are investigated by transmission electron microscopy (TEM). It is experimentally confirmed that the layers in the h-BN flakes are arranged in the AA' stacking. The wrinkles in a form of threefold network throughout the h-BN crystal are oriented along the armchair direction, and their formation mechanism was further explored by molecular dynamics simulations. Our findings provide a deep insight about the microstructure of h-BN and shed light on the structural design/electronic modulations of two-dimensional crystals.

cond-mat.mtrl-sci↗

arXiv2015

Thermal stability of a free nanotube from single-layer black phosphorus

Similar to the carbon nanotube fabricated from graphene sheet, a black phosphorus nanotube (BPNT) also can theoretically be produced by curling the rectangular single-layer black phosphorus (SLBP). In present study, the effect of thermal vibration of atoms on the failure of a BPNT is investigated using molecular dynamics simulations. Two types of double-shell BPNTs, which are obtained by curling the rectangular SLBP along its armchair/pucker direction and zigzag direction (in-plane normal) respectively, are involved in simulation. At finite temperature, a bond on the outer shell of tube is under tension due to both of curvature of tube and serious thermal vibration of atoms. As the length of a bond with such elongation approaches its critical value, i.e., 0.279 nm, or the smallest distance between two nonbonding phosphorus atoms is over 0.389nm caused by great variation of bond angle, the tube fails quickly. The critical stable states of either an armchair or a zigzag BPNT at finite temperature are calculated and compared. To achieve a stable BPNT with high robustness, the curvature of the tube should be reduced or the tube should work at a lower temperature. Only when the BPNT has structural stability, it has a potential application as a nanowire in a future nano electro-mechanical system (NEMS).

physics.comp-ph↗