AlN Compounds Research Articles

Interaction of Si Atom with the (001) Surface of TiN, AlN and TaN Compounds

Nowadays, the application of multicomponent coatings with multiphase nanocrystalline structure is the most promising direction in the search for wear-resistant protective coatings with a full set of necessary operational properties. Nanocrystalline multicomponent coatings based on the Ti-Al-Ta-Si-N system have a high hardness combined with thermal stability and oxidation resistance. Silicon atoms are weakly soluble in the TiN, Ti1−xAlxN, and TaN crystalline phases of the Ti-Al-Ta-Si-N system and interact preferentially with N atoms, forming the amorphous Si3N4 phase. In this context, it is important to first study the peculiarities of the interaction of Si atoms with the simplest structural units of the Ti-Al-Ta-Si-N system, such as TiN, AlN, and TaN compounds with the NaCl structure. This work is devoted to the study of the interaction of a Si atom with the (001) surface of AlN, TiN, and TaN compounds with the NaCl structure using ab initio calculations. This provides information for a deep understanding of the initial stages of the formation of different crystallites of the considered composite. It was established that the adsorption of silicon on the (001) surface of AlN, TiN, and TaN significantly increases the relaxation of the surface layers and leads to an increase in the corrugation observed on the clean surfaces. The largest corrugation is observed on the surface of the TaN compound. The most energetically favorable adsorption positions of Si atoms were found to be the position of Si above the N atom on the TiN and TaN surfaces and the quadruple coordinated position on the AlN surface. The valence electron density distribution and the crystal orbital Hamiltonian population were studied to identify the type of Si atom bonding with the (001) surface of AlN, TiN, and TaN compounds. It was found that silicon forms predominantly covalent bonds with the nearest metal and nitrogen atoms, except for the quadruple coordinated position on the surface of TiN and TaN, where there is a high degree of ionic bonding of silicon with surface atoms.

Analysis of AlN monolayer as a prospective cathode for aluminum-ion batteries

Developing cathode materials with high specific capability and excellent electrochemical performance is crucial for the advancement of aluminum-ion batteries, which leverage the high theoretical energy density of aluminum metal anodes. In this paper, we investigated the interaction of cluster and Al atom with AlN (−100) and (001) monolayer using density functional theory to assess the applicability of AlN as cathode material for aluminum-ion batteries. The results show that the AlN (001) monolayer is the most effective for adsorbing and accommodating clusters. Moreover, the AlN (001) monolayer maintains metallic behavior at different concentrations of the cluster, laying the foundation for its battery application. The theoretical storage capacity of the cluster is 105.93 which exceeds that of the Al/graphite battery. The formation energy of -intercalated AlN compounds is −2.74 eV, and the intercalant gallery height is moderate. Furthermore, the diffusion barrier of 0.19 eV for cluster between the AlN (001) monolayer provides high rate capability. The results indicate that AlN monolayer may be a potential cathode material for aluminum-ion batteries.

Pressure effect of optical properties of AlN, GaN, and InN Compounds

We present first-principles full-potential linearized augmented plane wave calculations of the effect of hydrostatic pressure on the optical properties of wurtzite GaN, InN and AlN compounds. The refractive index and its variation with hydrostatic pressure are well described. The accurate calculation of linear optical function (refraction index and its pressure derivative, and both imaginary and real parts of dielectric function) is performed in the photon energy range up to 30 eV. The predicted optical constant agrees well with the available experimental data.

Microstructure and corrosion resistance characteristics of Ti–AlN composite produced by selective laser melting

AbstractThe aim of this study is to produce Ti–AlN via selective laser melting. The results show that the microstructure of the produced alloy is not uniform. The X‐ray diffraction measurements show that the Ti–AlN composite is composed of a Ti matrix, AlN compounds, as well as (TiN)0.88, Al6Ti19, and Al1.1Ti0.9 intermetallics. The as‐printed Ti–AlN is also composed of dendrites of two typical titanium nitrides (TiN and Ti2N) and titanium aluminum nitride (Ti2AlN). Subsequent quenching and annealing slightly change the phase composition of the alloy and is the main reason for their different corrosion behaviors in acidic and chloride‐containing solutions. The results of this study show that the formation of Al‐rich ternary phases improved the corrosion resistance of the three‐dimensional‐printed Ti–AlN after quenching.

Surface modification and effects on tribology by laser texturing in Al2O3.

We investigate the surface modification by laser texturing and effects thereof on the tribological performance in Al2O3. By detailed observation for microstructure evolution, it has been shown that there were three distinct modification morphologies by laser treatment: dense surface microfeatures, "coral" dendritic structures, and coarse grains. X-ray diffraction (XRD) results indicated that there was no formation of metastable phases due to low supercooling in solidification in the nanosecond laser regime. The formation of AlN compounds in the laser-treated region was examined by using x-ray photoelectron spectroscopy (XPS), which led to dense surface microfeatures and randomly distributed pores formation in the laser treated region. The formation of "coral" dendritic structures on the edge of groove and coarse grains in the vicinity of the laser surface was attributed to the fast-cooling rates. Wear tests were carried out to analyze the effect of laser texturing on tribological performance. The results of coefficients of friction (COF) illustrated that laser texturing can significantly improve COFs for dry friction; however, it decreases the COFs for wet friction. The mechanism of wear was explained based on a SEM measurement for worn surfaces; the formation of surface texture can store abrasive particles and debris lead to hydrodynamic lubricant film formation and the COFs significantly reducing for wet friction.

Mechanical response, thermal conductivity and phononic properties of group III-V 2D hexagonal compounds

Two-dimensional hexagonal compounds have gained a lot of attention due to their potential application in energy, photovoltaics, mechanics and optoelectronics. In this work, we investigate the mechanical, thermal and phononic properties of group III-V binary compounds using ab-initio calculations. Pressure and strain dependency are also explored. The four compounds, BN, BP, AlN and AlP, are found to exhibit hyperelastic softening behavior and high interatomic rigidity that is highly desirable in the automotive and aeronautical industries. Besides an anisotropic elastic response that appears in the nonlinear regime and at non-zero pressure, the compounds contract when the temperature increases. The results related to thermal conductivity reveal the potential application of BN in thermal management. However, the high Grüneisen parameter and the high phonon sccatering rate render BP and AlN compounds good candidates for thermoelectric devices.

A novel TiC-based composite co-strengthened with AlN particulates and graphene nano-platelets

Fully dense TiC-based composites were produced by spark plasma sintering at 1900 °C with introducing AlN and graphene nano-platelets (GNPs) additives to the TiC matrix. The participation of AlN in removing oxygen-bearing species (i.e., TiO2) has been found to be explicable for boosting the sinterability of TiC. TiN was formed in-situ as a product of the chemical reaction between AlN and TiO2 compounds, dissolving within the TiC matrix and producing Ti(C,N) solid solution. Moreover, the co-addition of AlN and GNPs resulted in the creation of Al2OC as another in-situ phase. This compound together with the initially introduced additives activated grain refinement and dispersion strengthening mechanisms, uplifting the flexural strength of TiC by ~35% (standing at 703 MPa). Although the intragranular fracture was the predominant wear mode in the monolithic TiC, the synergetic impacts of AlN and GNPs additives altered the prevailing mode to intergranular.

Monte Carlo simulation study of electron yields from compound semiconductor materials

A systematic study has been performed based on a Monte Carlo simulation for the investigation of secondary electron yields, backscattering coefficients, and total electron yields for eight compound semiconductor materials, i.e., AlN, TiN, VN, VC, GaAs, InAs, InSb, and PbS, at different incident electron energies in the range 0.1–10 keV. Our Monte Carlo simulation model is based on the Mott cross section for electron elastic scattering as calculated by a partial wave method and a dielectric functional approach to electron inelastic scattering with the full Penn algorithm. We used Palik's optical data for lower photon energies below 100 eVs and Henke's data for higher photon energies. The cascade production of secondary electrons in electron inelastic scattering and low energy is included in the simulation. The simulated results of electron backscattering coefficients are compared with the experimental data available in the literature. Considering the fact that the experimental data for these compound materials are not available, we have compared them with experimental data for elements having the nearest mean atomic numbers. The simulation predicted much larger backscattering coefficient values than the empirical Staub formula.

An ab initio study of the structural and optoelectronic properties of AlxGa1−xN (x = 0, 0.125, 0.375, 0.625, 0.875, and 1) semiconductors

The structural and optoelectronic properties of AlxGa1−xN (x = 0, 0.125, 0.375, 0.625, 0.875, and 1) semiconductors are studied in detail by applying the full-potential linearized augmented plane-wave method in density functional theory in WIEN2k software. The lattice parameter, the bulk modulus, and its pressure derivative are calculated using the Perdew–Burke–Ernzerhof generalized gradient approximation and by fitting the calculated total energy to the Murnaghan equation. These parameters are found to be in excellent agreement with experimental and theoretical results for both the GaN and AlN compounds. For the Al0.125Ga0.875N, Al0.375Ga0.625N, Al0.625Ga0.375N, and Al0.875Ga0.125N alloys, because of the lack of the theoretical and experimental data, our results can be considered as first predictions. The Tran–Blaha modified Becke–Johnson approach (TB-mBJ) is applied to determine the optoelectronic properties. The results demonstrate that GaN and the AlxGa1−xN alloys with x = 0.125, 0.375, 0.625, and 0.875 have a direct Γ–Γ bandgap, whereas the binary AlN compound has an indirect Γ–X bandgap. Furthermore, the optical properties, such as the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss function, are presented and discussed in detail; their wide bandgap means that these compounds can be applied in optoelectronic devices for application in the main parts of the ultraviolet and visible spectrum.

Theoretical Investigation on Effect of Boron on Improving the Hardness of Zincblende-Aluminium Nitride and Its Mechanical, Thermal and Thermoelectric Properties

In this paper, we present the outcome of ab-initio band structure study carried out on cubic phase ternary BxAl1−xN (x = 0, 0.125, 0.25, 0.5, 0.75, 0.875, 1.0) alloys in order to analyze the elastic coefficients thereby the structural, thermoelectric, electronic, thermal, mechanical, and optical properties of these alloys. With the aim of enhancing the hardness of aluminium nitride (19 GPa), the present study on the proposed combinations reveal that B0.75Al0.25N (40.5 GPa) and B0.875Al0.125N (49.5 GPa) alloys turn out to be superhard materials as their hardness surpasses 40 GPa. Further, B0.875Al0.125N alloy has been identified to serve as a good thermoelectric as it has a high Seebeck coefficient value of 240 µV/K and of melting temperature of 4282 K. Except for the binary compounds AlN and BN, all the other ternary alloys are predicted to be direct band gap materials. The density of states, band structure, charge density plot, various elastic moduli, Debye’s temperature, elastic wave velocity, dielectric constant, Seebeck’s coefficient and other properties of interest are discussed in this paper. The results are compared and found to agree very well with the available literature.

Strain study of epitaxial Al1−xGaxN based on first-principles theory

The mechanical properties of Al1−xGaxN epitaxial layers grown on GaN and AlN substrates were studied by using density functional theory and anharmonic elastic calculation method. Accurate theoretical calculation of nonlinear elastic responses is a basic and important scientific question, which is the key to understand and further explore the potential synthesis and design of new solids. In this paper, detailed numerical calculations were carried out for the nonlinear mechanical properties of würtzite GaN and AlN compounds. The variation of strain energy and stress of disordered Al1−xGaxN epitaxial layer with gallium composition was analyzed. We found that in the epitaxial structure of AlN substrate, with the increase of gallium content, the influence of nonlinear effect on internal stress reached 29.4%, which proved the great influence of nonlinear mechanical response on semiconductor alloy material and heterostructure.

Laser gas assisted texturing and formation of nitride and oxynitride compounds on alumina surface: Surface response to environmental dust

Laser gas assisted texturing of alumina surface is carried out, and formation of nitride and oxynitride compounds in the surface vicinity is examined. The laser parameters are selected to create the surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the surface vicinity. This, in turn, lowers the free energy of the textured surface and enhances the hydrophobicity of the surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured surface. Some dry mud residues remain on the textured surface after the dry mud is removed by a pressurized desalinated water jet.

Theoretical Predictions of Structural, Electronic, and Optical Properties of Dilute Bismide AlN1−x Bi x in Zinc-Blend Structures

We report the results of first-principles calculations based on the full-potential linearized augmented plane wave (FP-LAPW + lo) method to explore the effects of alloying under the non-conventional AlN III–V compound with bismuth. We have calculated the structural and electronic properties of the binary compounds AlN and AlBi in the zinc blend structure. We have found a good agreement between our results and the experimental and theoretical results available for that binary compounds which may be a support for the results of the ternary alloys. For the AlNBi ternary alloys, we have found a rapid reduction of the energy gap by 1.31 eV/%Bi accompanied by a strong increase in the spin–orbit splitting energy (Δso) with increasing Bi composition. We have also shown that the Δso becomes greater than the energy gap for composition of Bi about 4.2% (Δso > Eg). This result is significant due to the possibility of suppressing Auger recombination, which is expected to improve the high temperature performance and thermal stability of light emitting devices. Finally, we have calculated the variation of the optical properties of AlNBi compounds, such as dielectric function and refractive index versus Bi composition.

Study on anisotropies and momentum densities in AlN, GaN and InN by positron annihilation

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalized positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8-N. Initial results show a clear asymmetrical positron charge distribution relative to the bond center. It is observed that the positron density is maximum in the open interstices and is excluded not only, from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001,110) planes. The results are used to analyze the positron effects in AlN, GaN and InN compounds. Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the twodimensional angular correlation of annihilation radiation (2D-ACAR).

Ab initio study of structural and electronic properties of (GaN)n/(AlN)n superlattices

Structural and electronic properties of binary GaN and AlN compounds and their superlattices (SLs) (GaN)n/(AlN)n are investigated using the first-principles full potential linear muffin-tin orbitals method (FP-LMTO). The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW). The ground-state properties are determined for the bulk materials GaN, AlN, and their superlattices (GaN)n/(AlN)n) in cubic phase. The calculated structural properties of GaN and AlN compounds are in good agreement with available experimental and theoretical data. It is found that AlN exhibit an indirect fundamental band gap while that GaN and the superlattices (SLs) exhibit a direct fundamental band gap, which might make the superlattices (GaN)n/(AlN)n materials promising and useful for optoelectronic applications. The fundamental band gap decreases with increasing the number of monolayer.

Ultrasensitive Thin-Film-Based Alx Ga1-x N Piezotronic Strain Sensors via Alloying-Enhanced Piezoelectric Potential.

Alx Ga1-x N thin-film-based piezotronic strain sensors with ultrahigh strain sensitivity are fabricated through alloying of AlN with GaN. The strain sensitivity of the ternary compound Alx Ga1-x N is higher than those of the individual binary compounds GaN and AlN. Such a high performance can be attributed to the piezoelectric constant enhancement via intercalation of Al atoms into the GaN matrix, the effect of residual strain, and a suppressed screening effect.

Laser gas assisted texturing of alumina surfaces and effects of environmental dry mud solution on surface characteristics

High pressure nitrogen gas assisted laser texturing of alumina surface is carried out and the effects of dust accumulation and mud formation on the surface characteristics are examined. The dust accumulation and mud formation is simulated in the laboratory environments in line with the local environmental conditions. Morphological and metallurgical changes in the laser treated region are examined using scanning electron and atomic force microscopes, energy dispersive spectroscopy, and X-ray diffraction. Surface microhardness is measured and residual stress formed in the surface region is determined from the X-ray diffraction data. Surface hydrophobicity is assessed through the contact angle measurements. Scratch tests are incorporated to measure the friction coefficient of the laser treated and as received workpiece surfaces. It is found that laser texturing results in superhyrophobic surface and the formation of AlN compounds at the textured surface lowers the surface energy while contributing to the surface hydrophobicity enhancement. The mud solution modifies the surface texture characteristics of the laser treated workpieces; in which case, surface hydrophobicity reduces significantly. Surface hardness increases considerably after the laser treatment process because of grain refinement under high cooling rates and volume shrinkage due to AlN compound formation in the surface region. Residual stress is compressive in the surface region of the laser textured workpiece and the mud solution increases slightly surface hardness and residual stress in the surface region.

DFT predictions of ferromagnetism in the AlC0.0625N0.9375 and AlC0.125N0.875 compounds

We employed density functional theory (DFT) in order to study the structural, electronic, and magnetic properties of pure AlN and C-atom-doped AlN compounds. The calculations were carried out using the method based on pseudopotential, employed exactly as implemented in Quantum ESPRESSO code. For the description of the electron–electron interaction, generalized gradient approximation (GGA) was used. The calculations showed that the substitution of a C atom at the N site introduce a magnetic moment of about 1.0μB, while two C atom substitutions introduce a magnetic moment of about 2.0μB. These magnetic properties become hybridization states C-2p and their first neighboring Al-2p and first neighboring N-2p atoms. Calculated magnetic properties indicate that C-doped AlN compound can potentially be used in diluted magnetic semiconductors.

Laser surface treatment of aluminum based composite mixed with B4C particles

Abstract Laser treatment of hot pressed mixture of aluminum (85 wt%) and B4C (15 wt%) is carried out. Metallurgical and morphological changes at the laser treated surface are examined using the analytical tools. Microhardness and fracture toughness of the workpiece surfaces are determined prior to and after the laser treatment process. Texture and hydrophobicity of the laser treated surface is assessed incorporating the atomic force microscopy and contact angle measurements. It is found that a dense layer consisting of fine grains of sub-micron sizes (0.8–0.4 μm) and B4C particles is formed at the laser treated surface. Microhardness increases at the laser treated surface because of the presence of the dense layer and the formation of AlN compounds at the surface. Fracture toughness of the laser treated surface reduces slightly because of the microhardness enhancement at the surface. The textures of the laser treated surface compose of micro/nano poles, which result in higher contact angles than that of the untreated surface, and formation of AlN compound adds to the surface hydrophobicity enhancements.

Structural and elastic properties of TiN and AlN compounds: first-principles study

Abstract First-principles calculations of the lattice constants, bulk modulus, pressure derivatives of the bulk modulus and elastic constants of AlN and TiN compounds in rock-salt (B1) and wurtzite (B4) structures are presented. We have used the fullpotential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the generalized gradient approximation (GGA) for the exchange-correlation functional. Moreover, the elastic properties of cubic TiN and hexagonal AlN, including elastic constants, bulk and shear moduli are determined and compared with previous experimental and theoretical data. Our results show that the structural transition at 0 K from wurtzite to rock-salt phase occurs at 10 GPa and −26 GPa for AlN and TiN, respectively. These results are consistent with those of other studies found in the literature.