GaN Haeckelite Single-Layered Nanostructures: Monolayer and Nanotubes.

Dulce C Camacho-Mojica,Florentino López-Urías

doi:10.1038/srep17902

Dulce C Camacho-Mojica, Florentino López-Urías

Open Access

https://doi.org/10.1038/srep17902

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Abstract

Nowadays, III-V semiconductors are interesting candidate materials for the tailoring of two dimensional (2D) graphene-like structures. These new 2D materials have attracted profound interest opening the possibility to find semiconductor materials with unexplored properties. First-principles density functional theory calculations are performed in order to investigate the electronic properties of GaN planar and nanotube morphologies based on Haeckelite structures (containing octagonal and square membered rings). Optimized geometries, band-structures, phonon dispersion, binding energies, transmission electron microscopy images simulations, x-ray diffraction patterns, charge densities, and electronic band gaps are calculated. We demonstrated that GaN Haeckelite structures are stable exhibiting a semiconducting behavior with an indirect band gap. Furthermore, it was found that GaN Haeckelite nanotubes are semiconductor with a band gap nature (direct or indirect) that depends of the nanotube´s chirality and diameter. In addition, it was demonstrated that surface passivation and the interaction with hydrazine, water, ammonia, and carbon monoxide molecules can change the band-gap nature. Our results are compared with the corresponding GaN hexagonal honeycomb structures.

Highlights

One of the most famous prototypes of layered materials is graphene, which is a perfect two dimensional system with a single atom thickness[1,2]
After geometry optimization on the single layer systems, the monolayers (Haeckelite and honeycomb) become flat as was previously reported for GaN and others III-V compounds with a honeycomb structure[20]
We have investigated the electronic properties of GaN planar and nanotube structures with honeycomb and Haeckelite structure

Summary

Computational details

Electronic calculations were performed using Density Functional Theory[40,41]. All atoms contained in the systems are relaxed using conjugated gradient method and the total energy was calculated when the forces were converged to less than 0.04 eV/Å. The binding energy is determined by means of Ebind = E(system) – nE(Ga) – nE(N),where E(system) is the total energy of GaN nanotubes or monolayers. Ebind refers to the necessary energy to split into individual atoms from the nanotube or monolayer systems. The cohesion energy was calculated as follows: Ea = ET – EG – EM, where ET corresponds to the energy of GaN monolayer with a gas molecule adsorbed. EG and EM correspond to energies of isolated GaN monolayer and gas molecule respectively. Negative values of Ea mean that the molecule is absorbed by GaN monolayer

Results and Discussion

Conclusions

Additional Information