Gallium Nitride Nanosheets Research Articles

Numerical Evaluation of the Elastic Moduli of AlN and GaN Nanosheets.

Two-dimensional (2D) nanostructures of aluminum nitride (AlN) and gallium nitride (GaN), called nanosheets, have a graphene-like atomic arrangement and represent novel materials with important upcoming applications in the fields of flexible electronics, optoelectronics, and strain engineering, among others. Knowledge of their mechanical behavior is key to the correct design and enhanced functioning of advanced 2D devices and systems based on aluminum nitride and gallium nitride nanosheets. With this background, the surface Young's and shear moduli of AlN and GaN nanosheets over a wide range of aspect ratios were assessed using the nanoscale continuum model (NCM), also known as the molecular structural mechanics (MSM) approach. The NCM/MSM approach uses elastic beam elements to represent interatomic bonds and allows the elastic moduli of nanosheets to be evaluated in a simple way. The surface Young's and shear moduli calculated in the current study contribute to building a reference for the evaluation of the elastic moduli of AlN and GaN nanosheets using the theoretical method. The results show that an analytical methodology can be used to assess the Young's and shear moduli of aluminum nitride and gallium nitride nanosheets without the need for numerical simulation. An exploratory study was performed to adjust the input parameters of the numerical simulation, which led to good agreement with the results of elastic moduli available in the literature. The limitations of this method are also discussed.

Piezoelectricity in wide bandgap semiconductor 2D crystal GaN nanosheets.

Gallium nitride (GaN) exhibits various potential applications in optics and optoelectronics due to its outstanding physical characteristics, including a wide direct bandgap, strong deep-ultraviolet emission, and excellent electron transport properties. However, research on the piezoelectric and related properties of GaN nanosheets are scarce, as previous small-scale GaN investigations have mainly concentrated on nanowires and nanotubes. Here, we report a strategy for growing 2D GaN nanosheets using chemical vapor deposition on Ga/W liquid-phase substrates. Additionally, utilizing scanning probe techniques, it has been observed that 700 nm-thick GaN nanosheets demonstrate a piezoelectric constant of deff33 = 1.53 ± 0.21 pm V-1 and possess the capability to effectively modulate the Schottky barrier. The piezoelectric characteristics of 2D GaN are offering new options for innovative applications in various fields, including energy harvesting, electronics, sensing, and communications.

Adsorption of HCN, HNC and CH3CN toxic gases on the M-doped (M = Cr, Fe, Ni and Zn) GaNNS: A DFT-D study

In this work, the performance of transition metal-doped gallium nitride nanosheets (M-GaNNSs, M = Cr, Fe, Ni and Zn) for adsorption and sensing of HCN, HNC and CH3CN toxic gases were investigated at the Grimme-corrected Perdew–Burke-Ernzerhof/double numerical plus polarization (PBE/DNP) level of theory. The electronic properties, structural parameters, adsorption energies, density of states (DOS) curves, band gap energies and charge transfer values were analyzed to find the ability of eight metal-doped GaNNS in adsorbing and sensing HCN, HNC and CH3CN gases. Compared with pure GaNNS, in all eight metal-doped configurations, the adsorption energies were increased after the doping of metals, especially their value in 2-HCN-FeNGaNNS, 2-HNC-FeNGaNNS and 2-CH3CN-FeNGaNNS were greater than in others. Therefore, the FeNGaNNS may be a suitable candidate for adsorbing and removing all the three studied gases from the atmosphere. Upon adsorption of HCN, HNC and CH3CN gases on the metal-doped GaNNS, a significant change in the energy gap is found in 2-HCN-CrNGaNNS, 1-HNC-FeGaGaNNS and 2-CH3CN-CrNGaNNS complexes, and, in turn, in the conductivity of nanostructures. Therefore, it is predicted that, CrNGaNNS for sensing HCN and CH3CN gases and FeGaGaNNS for sensing HNC gas have a high potential. Although, FeGaGaNNS could be a good sensor for HCN and CH3CN gases in the second step and after CrNGaNNS.

HEXAGONAL HONEYCOMB PL-GaN NANOSHEET AS ADSORBENT SURFACE FOR GAS MOLECULES SENSING: A QUANTUM CHEMICAL STUDY

Regarding two-dimensional (2D) nanomaterials as gas sensors, we have studied the adsorption of gas molecules (NH3, NO2, NO) on the graphitic GaN sheet (PL-GaN) using density functional theory calculations. “Langmuir” adsorption of gas molecules of NH3, NO2, and NO on the graphitic GaN sheet has been accomplished using density functional theory. The changes in charge density have shown a more important charge transfer on the hexagonal honeycomb nanosheet of gallium nitride (GaN) which acts as the electron acceptor while gas molecules act as the stronger electron donors through adsorption on the graphitic-like GaN surface. The adsorption of NH3, NO[Formula: see text] and NO, respectively, on GaN nanosheet has more contribution with high expansion curves of hydrogen, nitrogen and oxygen. The results extracted from PDOS curves after optimization show the electron transferring from nitrogen and oxygen of gas molecules (adsorbate/donor) towards gallium in the active site of GaN surface (adsorbent/acceptor). GaN nanosheet represents enough capability for adsorbing gases of NH3, NO2, and NO through charge transfer from nitrogen and oxygen atoms to the gallium atom regarding the intra-atomic and interatomic interactions. Concerning the change of physicochemical properties of the PL-GaN sheet before and after molecule adsorption, the PL-GaN nanosheet can be applied as an appropriate selective gas sensor for NH3, NO2 and NO detection.

Adsorption and sensing of CS2, H2S and COS gases by pure and metal (Cr, Fe, Ni and Zn) doped GaN nanosheets: a DFT-D study

ABSTRACT The performance of the pure and metal (Cr, Fe, Ni and Zn) doped gallium nitride nanosheets (GaNNSs) for adsorption and sensing of CS2, H2S and COS gases were scrutinised at the Grimme-corrected PBE/DNP level of theory. The range of adsorption energies for CS2 gas was between −5.51 to −16.57 kcal mol−1 for MGa-GaNNS and −18.32 to −65.02 kcal mol−1 for MN-GaNNS so that the highest CS2 adsorption capability was predicted for CrNGaNNS. Based on the adsorption energies for H2S gas (−3.70 to −10.17 kcal mol−1 for MGa-GaNNS and −9.93 to −53.40 kcal mol−1 for MN-GaNNS), CrNGaNNS was estimated to be more suitable for H2S adsorption. The adsorption energies for COS gas on the MGa-GaNNS (−6.26 to −9.18 kcal mol−1) were smaller than those found for MN-GaNNS (−9.83 to −40.80 kcal mol−1), indicating that the capability of FeNGaNNS for COS adsorption is greater than other doped-GaNNSs. From the calculated electronic properties of doped-GaNNSs, it was found that FeNGaNNS could be more suitable for sensing CS2 and H2S gases and CrNGaNNS for the detection of COS gas. The results of the present research make predictions about the most promising systems for sensing and capturing CS2, H2S and COS toxic gases.

Low-temperature one-step solid state chemical synthesis of GaN nanosheets for conquering polysulfides in Li–S battery

Gallium nitride (GaN) nanosheets have been prepared as an active material for conquering polysulfides in Lithium–Sulfur (Li–S) batteries via one simple synthetic route at 550 °C. The process was carried out in a stainless steel autoclave by using gallium nitrate hydrate, sodium amide and metallic lithium as starting materials. The product was proven to be hexagonal GaN nanosheets by combined X-ray powder diffraction (XRD) pattern and Scanning electron microscopy (SEM). The GaN nanosheets were then used to coat on the Li–S battery separator, and the result proves an effective inhibition of the shutting problem and gives excellent electrochemical properties compared with traditional separators or GaN additives. The battery assembled by GaN coated separator shows good cycling stability with 408 mAh/g and a low capacity fading of 0.6‰ per cycle from 11th to 480th cycle at 2 C due to high utilization of the sulfur-based active species.

Transition metals (Fe, Ni and Zn) doped GaN nanosheets and their adsorption performance towards SO2 and NO2 toxic gases: A DFT-D approach

The emissions of SO2 and NO2 gases in the atmosphere through different sources can cause environmental problems such as air pollution and acid rain. The electronic properties of gallium nitride nanosheets (GaNNSs) as a semiconductor material can be tuned by transition metals doping. In this work, the adsorption performance of M (M = Fe, Ni and Zn) doped gallium nitride nanosheets (GaNNSs) towards SO2 and NO2 toxic gases were scrutinized by dispersion corrected density functional theory (DFT-D) calculations at PBE-D/DNP level of theory. Specific attention is paid to obtaining insights into the adsorption and sensing features of pristine and M-doped GaNNSs (MGa,N-GaNNS) towards SO2 and NO2 molecules. The energies of adsorption were calculated to be −27.2 kcal mol−1 for SO2-GaNNS and −11.8 kcal mol−1 for NO2-GaNNS complexes. The range of adsorption energies on the M-doped GaNNSs was −8.9 (NO2-ZnGa-GaNNS) to −72.1 (NO2–FeN-GaNNS) and −19.7 (SO2-FeGa-GaNNS) to −51.0 (SO2–FeN-GaNNS) kcal mol−1, indicating that FeN-GaNNS is energetically more favorable than other M-doped GaNNSs for NO2 and SO2 adsorption. The changes in the energy gaps of adsorption complexes revealed that the ZnN-GaNNS and ZnGa-GaNNS could be suitable better for sensing NO2 and SO2 gases, respectively. The present results are helpful not only to understand the adsorption nature of the NO2 and SO2 gases on M-doped GaNNS but also can provide helpful guidance for developing GaN-based sensors.

Adsorption behaviour of NO, NO2, CO and CS2 molecules on the surface of carbon-doped gallium nitride nanosheet: A DFT study

The adsorption behaviours of NO, NO2, CO and CS2 toxic gas molecules on the surface of carbon-doped gallium nitride nanosheet (CN-GaNNS) are investigated at the Grimme-corrected PBE/double numerical plus polarization (DNP) level of density functional theory. It is found that NO, CO and NO2 gas molecules are chemisorbed and CS2 gas molecule is physisorbed on CN-GaN sheet while they retain their molecular forms. The amounts of charge transfer upon adsorption of NO gas molecule on the surface of CN-GaNNS is more than NO2, CO and CS2. Upon adsorption of NO and NO2 on the CN-GaNNS, the significant change in the energy gap is found in NOCN-GaNNS and NO2CN-GaNNS complexes, and in turn, in the conductivity of nanostructures. Our study suggests that the CN-GaNNS based sensor has a high potential for NO and NO2 detection due to the significant change in conductance, as well as removing these toxic gases because of suitable adsorption energy. In addition, from the significant change in N–O bond length of NO gas upon adsorption, it is anticipated that CN-GaNNS could be used for catalysing NO gas.

Electronic structures and transport properties of low-dimensional GaN nanoderivatives: A first-principles study

Low-dimensional gallium nitride (GaN) nanoderivatives have recently attracted great attention, and they are one of the most attractive fields for future development of microelectronic devices. Here, the electronic structures and transport properties of GaN nanoderivatives were investigated by density functional theory. For two-dimensional bilayer GaN nanosheets, we found that AA-NN(GaGa) is the most stable structure among the five GaN stacking structures, and the stacking arrangement does not change the wide and indirect band gap of these two-dimensional bilayer stacked nanosheets. The transport properties of one-dimensional GaN nanoribbons were also investigated. The current in the bilayer GaN nanodevices was about twice that in the monolayer GaN nanodevices regardless of the nanoribbon morphology. That is, the bilayer GaN nanodevices show the current superposition law, like a parallel circuit, compared with their respective monolayer GaN model devices. The one-dimensional armchair boundary GaN nanoribbon devices showed the width effect because the width had a great effect on the current–voltage (I-V) curve and transport characteristics, but the one-dimensional zigzag boundary GaN nanoribbon devices did not and the I-V characteristic curves for different nanoribbon widths were similar. These extraordinary electronic structures indicate that GaN is promising for application in microelectronic devices.

Theoretical investigation of nitric oxide adsorption on the surface of pure and metal (Ti, Cr, Fe, Ni and Zn) doped gallium nitride nanosheets

Abstract In this work, the electronic properties of gallium nitride nanosheets (GaNNSs) as a semiconductor can be tuned by transition metals (TM = Ti, Cr, Fe, Ni and Zn) doping for adsorbing of nitric oxide molecule at Grimme-corrected PBE/double numerical plus polarization (DNP) level of theory. Here, five TMs were located instead of Ga or N atoms to increase the adsorption efficiency. The calculated adsorption energies were in the range of −3.36 to −8.81 kcal/mol for pristine GaNNS and −25.50 to −95.92 kcal/mol for TM-doped GaNNS, indicating that TM doping increased the adsorption energy of NO gas. Between the studied complexes, the NO–CrN-GaNNS (−95.92 kcal/mol) displayed considerably enhanced adsorption energy relative to the pure GaNNS (−8.81 kcal/mol). The energy gaps which are manipulated by TM doping decreased in the range of 0.06–1.84 eV upon adsorption of NO gas. Thus, the doped GaNNS could be an excellent candidate for removing NO gas from the environment.

Adsorption performance of M-doped (M = Ti and Cr) gallium nitride nanosheets towards SO2 and NO2: a DFT-D calculation.

The structure, adsorption characteristics, electronic properties, and charge transfer of SO2 and NO2 molecules on metal-doped gallium nitride nanosheets (M-GaNNSs; M = Ti and Cr) were scrutinized at the Grimme-corrected PBE/double numerical plus polarization (DNP) level of theory. Two types, MGa-GaNNSs and MN-GaNNSs, of doped nanostructures were found. The MGa sites are more stable than the MN sites. The results showed that adsorption of SO2 and NO2 molecules on TiGa,N-GaNNSs is energetically more favorable than the corresponding CrGa,N-GaNNSs. The stability order of complexes is energetically predicted to be as NO2–TiGa-GaNNS > NO2–TiN-GaNNS > SO2–TiGa-GaNNS > NO2–CrN-GaNNS > SO2–TiN-GaNNS > NO2–CrGa-GaNNS > SO2–CrN-GaNNS > SO2–CrGa-GaNNS. The electron population analysis shows that charge is transferred from MGa,N-GaNNSs to the adsorbed gases. The TiGa-GaNNS is more sensitive than the other doped nanostructures to NO2 and SO2 gases. It is estimated that the sensitivity of TiGa-GaNNS to NO2 gas is more than to SO2 gas.

The Effect of Functionalization on Spin-Polarized Transport of Gallium Nitride–Based Magnetic Tunnel Junctions

Using first-principles spin-polarized density functional theory computations, the effect of functionalization (fluorination and hydrogenation) on spin-polarized transport of gallium nitride (GaN) nanosheet–based magnetic tunnel junction (MTJ) with CrO2 as electrodes is investigated. The results show fluorinated GaN–based structure exhibits better spin filtration and high TMR (maximum ~ 99%), as compared with hydrogenated GaN (maximum TMR ~ 93%)– and pristine GaN (maximum TMR ~ 83%)–based structures. In addition, fluorinated GaN nanosheet exhibits a ferromagnetic behavior with a magnetic movement of 1.0 μb per fluorine atom. The magnetic movements for pristine GaN and hydrogenated GaN sheets are reported to be 0 μb and 0.9 μb per hydrogen atom, respectively. Higher TMR, better spin filtration, and ferromagnetic behavior for fluorinated GaN–based structure open up its possibility as spin filter (injector) in MTJs and other spin-based devices.

Exploring the adsorption of CO toxic gas on pristine and M-doped (M = Ti, Cr, Fe, Ni and Zn) GaN nanosheets

The capability of pristine and M-doped (M = Ti, Cr, Fe, Ni and Zn) gallium nitride nanosheets (M-GaNNS) was explored at the Grimme-corrected PBE/double numerical plus polarization (DNP) level of theory for adsorbing and sensing of the carbon monoxide (CO) molecule.

Molecular dynamics simulations of gallium nitride nanosheets under uniaxial and biaxial tensile loads

Molecular dynamics (MD) simulations are employed to study the elastic properties of gallium nitride (GaN) nanosheets. Young’s and bulk moduli of GaN nanosheets with different side lengths and height/width ratio are obtained. Besides, the configuration of the nanosheet at different strains is represented until the fracture initiation and final fracture are observed. It is seen that the zigzag nanosheets have larger elastic moduli than armchair ones with the same sizes. Moreover, increasing the length size of the nanosheets results in decreasing Young’s modulus. Bulk moduli of GaN nanosheets are also obtained by applying biaxial loading on all edges. It is seen that under the biaxial tensile force, the fracture is initiated at the nanosheet corners and is continued toward the nanosheet center. A nonlinear relation between the bulk modulus and nanosheet size is observed.

Graphene-Oxide-Assisted Synthesis of GaN Nanosheets as a New Anode Material for Lithium-Ion Battery.

As the most-studied III-nitride, theoretical researches have predicted the presence of gallium nitride (GaN) nanosheets (NSs). Herein, a facile synthesis approach is reported to prepare GaN NSs using graphene oxide (GO) as sacrificial template. As a new anode material of Li-ion battery (LIBs), GaN NSs anodes deliver the reversible discharge capacity above 600 mA h g-1 at 1.0 A g-1 after 1000 cycles, and excellent rate performance at current rates from 0.1 to 10 A g-1. These results not only extend the family of 2D materials but also facilitate their use in energy storage and other applications.

Force constants of BN, SiC, AlN and GaN sheets through discrete homogenization

The force constants related to the bond stretching and angular variation of boron nitride, silicon carbide, aluminium nitride and gallium nitride nanosheets are directly evaluated from ab-initio reference solutions of the Young’s modulus and the Poisson’s ratio. To this end, the analytical expressions of the elastic constants of a generic monolayer hexagonal diatomic sheet are derived, starting from its sticks-and-springs molecular mechanics model, through proper tools of the homogenization of periodic discrete media. Numerical benchmark assessments are given.

On the effect of vacancy defect on the mechanical properties of gallium nitride nanosheets

Using molecular dynamics (MD) simulations, the influence of the vacancy defects on the mechanical properties of gallium nitride (GaN) nanosheets is investigated. Two types of defective nanosheets are studied. In one of them, only one atom is removed at the vacancies and in the other, the number of removed atoms is not limited. It is shown that GaN nanosheets with multiple vacancies have larger in-plane elastic modulus than nanosheets with single vacancies. Besides, the ultimate stress and strain of GaN nanosheets are computed. Compared to perfect nanosheet, a significant decrease is observed in the ultimate stress of GaN nanosheet with only 2% defect. By plotting the fracture evolution of nanosheets under uni-directional tensile loading, three different patterns are observed. Moreover, by using bi-directional tensile tests on the nanosheets, the bulk moduli of perfect and defective GaN nanosheets are computed.

Strain field tuning the electronic and magnetic properties of semihydrogenated two-bilayer GaN nanosheets

In this paper, first-principles calculations based on the density functional theory, are performed to investigate the effects of strain field on the electronic and magnetic properties of two-bilayer gallium nitride (GaN) nanosheets. The two-bilayer GaN nanosheet without surface modification forms a planar graphitic structure, whereas that with full hydrogenation for the surface Ga and N atoms adopts the energetically more favorable wurtzite structure. Surface hydrogenation is proven to be an effective way to induce a transition from indirect to direct band gap. The bare and fully-hydrogenated GaN nanosheets are nonmagnetic semiconductors. When only one-side Ga or N atoms on the surface are hydrogenated, the semihydrogenated two-bilayer GaN nanosheets will preserve their initial wurtzite structures. The two-bilayer GaN nanosheet with one-side N atoms hydrogenated transforms into a nonmagnetic metal, while that with one-side Ga atoms hydrogenated (H-GaN) is a ferromagnetic semiconductor with band gaps of 3.99 and 0.06 eV in the spin-up and spin-down states, respectively. We find that the two-bilayer H-GaN nanosheets will maintain ferromagnetic states under a strain field and the band gaps Eg in spin-up and spin-down states are a function of strain . As the tensile strain is +6%, the band gap in spin-up state reduces to 2.71 eV, and that in spin-down state increases to 0.41 eV for the two-bilayer H-GaN nanosheets. Under the compressive strain field, the two-bilayer H-GaN nanosheets will show a transition from semiconducting to half-metallici state under compression of -1%, where the spin-up state remains as a band gap insulator with band gap of 4.16 eV and the spin-down state is metallic. Then the two-bilayer H-GaN nanosheets will turn into fully-metallic properties with bands crossing the Fermi level in the spin-up and spin-down states under a compressive strain of -6%. Moreover, the value of binding energy Eb for the two-bilayer H-GaN nanosheet decreases (increases) monotonically with increasing compressive (tensile) strain. It is found that although hydrogenation on one-side Ga atoms of the two-bilayer H-GaN nanosheets is preferred to be under compressive strain, the two-bilayer H-GaN nanosheets are still the energetically favorable structures. The physical mechanisms of strain field tuning band gaps in the spin-up and spin-down states for the two-bilayer H-GaN nanosheets are mainly induced by the combined effects of through-bond and p-p direct interactions. Our results demonstrate that the predicted diverse and tunable electronic and magnetic properties may lead to the potential application of GaN nanosheets in novel electronic and spintronic nanodevices.

Mechanical behavior of gallium nitride nanosheets using molecular dynamics

Gallium nitride (GaN) nanostructures have applications in optoelectronics and other allied nanoelectronic devices like nanosensors and nanogenerators. The stability and reliability of a GaN nanosheet is related to its mechanical behavior under external loads. The presence of defects influences the mechanical behavior of such structures. In this article, classical molecular dynamics simulations were performed by employing the Stillinger–Weber potential on a system of single layer nanosheet of GaN containing single and double atomic vacancy defects. The stress–strain responses show that, the fracture limit decreases due to the presence of such defects when compared with pristine GaN nanosheets. The fracture process of such nanosheet with single atomic vacancy has been illustrated. The effect of separation distance of the divacancies on the fracture stress, fracture strain and the Young’s modulus were investigated. In addition, the effect of strain rates on the failure stress and strain of pristine GaN nanosheet has also been studied.