Beryllium Nitride Research Articles

Combination of Ambient and High‐Temperature Beryllium Nitride Motifs in W2Be4N5 and W4Be8N9

Compounds of transition metals and beryllium have a wide range of applications, from everyday tools to high tech applications. Remarkably, no single ternary beryllium nitride with a transition metal is known. Here, we report on the synthesis and properties of the first transition metal nitridoberyllates, namely W2Be4N5 and W4Be8N9. Both compounds were synthesized in a high‐temperature high‐pressure approach from Be3N2 and W, using azide generated N2 as an oxidizing agent. The crystal structures, consisting of alternating layers of WN6 trigonal prisms and BeN4 tetrahedra, were elucidated by single‐crystal X‐ray diffraction (sc‐XRD). The separating nitridoberyllate layers show either ambient temperature (α‐Be3N2 type) or high temperature (β‐Be3N2 type) motifs. W2Be4N5 was further corroborated by infrared (IR), nuclear magnetic resonance (NMR) and UV‐VIS spectroscopy and vibrating sample magnetometry (VSM) measurements. The latter revealed a mixed valence with an intermediate oxidation state of 3.5 for the W atoms. Both, the synthesis of the first transition metal nitridoberyllates and the synthesis approach using elemental W pave the way to a new field of nitride chemistry.

Combination of Ambient and High-Temperature Beryllium Nitride Motifs in W2Be4N5 and W4Be8N9.

Compounds of transition metals and beryllium have a wide range of applications, from everyday tools to high tech applications. Remarkably, no single ternary beryllium nitride with a transition metal is known. Here, we report on the synthesis and properties of the first transition metal nitridoberyllates, namely W2Be4N5 and W4Be8N9. Both compounds were synthesized in a high-temperature high-pressure approach from Be3N2 and W, using azide generated N2 as an oxidizing agent. The crystal structures, consisting of alternating layers of WN6 trigonal prisms and BeN4 tetrahedra, were elucidated by single-crystal X-ray diffraction (sc-XRD). The separating nitridoberyllate layers show either ambient temperature (α-Be3N2 type) or high temperature (β-Be3N2 type) motifs. W2Be4N5 was further corroborated by infrared (IR), nuclear magnetic resonance (NMR) and UV-VIS spectroscopy and vibrating sample magnetometry (VSM) measurements. The latter revealed a mixed valence with an intermediate oxidation state of 3.5 for the W atoms. Both, the synthesis of the first transition metal nitridoberyllates and the synthesis approach using elemental W pave the way to a new field of nitride chemistry.

DFT investigation on the design and optimization of icosahedral and octahedral beryllium nitride (Be3N2)x fullerene analogue. A comparative study with isosymmetry carbon fullerene

In this contribution, based on density Functional Theory, we focus on studying the structural and dynamic stability of octahedral and icosahedral beryllium nitride (Be3N2)x fullerenes and their symmetry equivalent carbon molecules. The icosahedron structure of beryllium nitride and carbon-based fullerenes shows hybrid features, between a sphere and a polyhedron. Nevertheless, the cohesive energies of carbon fullerenes are slightly lower than those of beryllium nitride based on Be3N2 units. Although icosahedral Ih (1,1) and Ih (2,2) (Be3N2)30 and (Be3N2)120 are energetically slightly less favorable than their corresponding carbon fullerenes, they showed chemically stable structures. IR & Raman spectra are also simulated using a coupled-perturbed KS/HF scheme permitting their identification. Importantly, no imaginary frequency is recorded in their vibrational spectra which confirms an inherent dynamic stability. These results provide valuable insights that can be extrapolated to other noncarbon nanostructures containing pentagonal rings or pentagonal defects.

Beryllium nitride (Be3N2) graphene like monolayer and zigzag single walled nanotubes. A DFT exploration of their structural and vibrational properties

Beryllium nitride (Be3N2) graphene like monolayer and zigzag single walled nanotubes. A DFT exploration of their structural and vibrational properties

Сравнительное исследование термостойкости пелликлов на основе бериллия

We demonstrate the possibility of manufacturing Be-based ultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be, ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of the absorbed power at which over a short period (tens of minutes) of vacuum annealing, initially sagging free-standing films became visibly stretched over the hole. Of the film structures tested here, the Be/BexNy structure (with beryllium nitride interlayers) showed the highest threshold for the absorbed power (1 W/cm2). However, due to the low strength of this structure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for the manufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Be and Be ultrathin films showed that they could withstand 24 hours of vacuum heating at an absorbed power density of 0.2 W/cm2 (film temperature ~250°C) without noticeable changes in EUV transmission or sagging of films. With comparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayer Mo/Be structure with a thickness of 30 nm appears to be preferable, as it shows less brittleness than a monolayer Be film with a thickness of 50 nm.

Comparative study of the thermal stability of Be-based extremeultraviolet pellicles

We demonstrate the possibility of manufacturing Be-basedultrathin films with high transmission at wavelengths of 11.4 and 13.5 nm. For free-standing films of Be and Be-based multilayer structures (Si/Be,ZrSi2/Be, Be/BexNy, Zr/Be, Ru/Be, Mo/Be), we determine the thresholds of theabsorbed power at which over a short period (tens of minutes) of vacuumannealing, initially sagging free-standing films became visibly stretchedover the hole. Of the film structures tested here, the Be/BexNy structure(with beryllium nitride interlayers) showed the highest threshold for theabsorbed power (1 W/cm2). However, due to the low strength of thisstructure, ZrSi2/Be, Mo/Be, and Be films seem to be more promising for themanufacture of a full-size pellicle. Long-term vacuum annealing of Mo/Beand Be ultrathin films showed that they could withstand 24 hours of vacuumheating at an absorbed power density of 0.2 W/cm2 (film temperature 250oC)without noticeable changes in EUV transmission or sagging of films. Withcomparable transmission (~83% at 13.5 nm and ~88% at 11.4 nm), a multilayerMo/Be structure with a thickness of 30 nm appears to be preferable, as itshows less brittleness than a monolayer Be film with a thickness of 50 nm. Keywords: Be-based pellicle, multilayer thin film, EUV lithography,thermal stability\

First principles study of electronic structure and optical properties of beryllium nitride in β phase (β-Be3N2)

Within the framework of density functional theory, electronic structure of beryllium nitride in β phase (β-Be3N2) is determined, and on the base of the electric structures, a number of key optical properties of β-Be3N2 are calculated, with the method of full-potential linearized augmented plane wave under the random phase approximation for the boundaries and the generalized gradient approximation for the exchange-correlation potentials. The calculated optical properties as a function of frequency include the real and imaginary parts of the dielectric function ε(ω), the refraction index n(ω), the extinction coefficient κ(ω), the reflectivity R(ω), the energy loss function L(ω), and the absorption coefficient I(ω) along the a and c directions of the primitive cell presenting the β-Be3N2 crystals. It is demonstrated that the optical properties of β-Be3N2 appear anisotropic for energies <35 eV, within the range of ultraviolet, and the p orbitals of nitrogen play the major role in relevant optical transitions.

DFT studies of hydrogen retention in beryllium nitride

The valence band density of states of bulk beryllium nitride (alpha-Be3N2) and the solvation energy of hydrogen atoms in this nitride is herein studied using the generalized gradient approximation density functional theory. The DOS is compared to photoelectron spectroscopy investigations of nitrogen-implanted beryllium. The presence of defects (atomic vacancies) was taken into consideration in the calculations on the trapping of deuterium. The barriers of activation for hydrogen atom diffusion in the bulk and from the defect were calculated and compared to their values in pure beryllium metal and in beryllium oxide. Some consequences regarding the effects of nitrogenation of beryllium as a plasma-facing material in nuclear fusion devices are eventually proposed.

The chemical state plot for beryllium compounds

Herein we report the construction of a Wagner chemical state plot for beryllium containing the: metallic, oxide, nitride and carbide forms of beryllium by combining electron beam induced AES and XPS data. AES and XPS values were collected from metallic beryllium mechanically abraded in vacuum, bulk and native beryllium oxide and homogeneous secondary-phase beryllium nitride and beryllium carbide inclusions. XPS data for beryllium nitride and carbide were obtained from the literature.

Analysis of the Be KLL Auger Transition of Beryllium Nitride and Beryllium Carbide by AES

Secondary phase particles of beryllium nitride and beryllium carbide in beryllium were analyzed by Auger Electron Spectroscopy. Survey spectra as well as high resolution Be KLL, N KLL and C KLL transitions were collected and are presented. The primary beryllium KLL Auger transitions for the nitride and carbide were recorded at 96.7 and 100.4 eV respectively. The homogeneity and composition of the secondary phase particles was confirmed by energy dispersive x-ray spectroscopy.

Synthesis and characterization of highly luminescent beryllium nitride

Highly luminescent beryllium nitride powder (Be3N2) has been synthesized by direct nitridation of metallic beryllium with ultra-high purity ammonia (NH3) in a horizontal quartz tube reactor at 1100°C. The calculated Gibbs free energy for this reaction at 1100°C is −602.20kJ/mol and the equilibrium constant is 2.7×1022, this make workable the process at the conditions chosen for this synthesis. The Be3N2 produced by this method is a light-gray powder which showed the typical high hardness of this material. The Be3N2 powders synthesized in this research consist mostly of agglomerates formed of regular cubic polyhedrons between one and two microns long each as shown by electron microscopy. These crystallites have a cubic structure as shown by X-ray diffraction and exhibit high intensity room temperature cathodoluminescence with a peak around 356nm (3.48eV), which is related to their near-band-edge emission. These properties make this material a strong candidate for wide-band optoelectronic applications such as ultraviolet-lasers, sensors and light-emitting diodes.

Properties of nitrogen-implanted beryllium and its interaction with energetic deuterium

Recent successful experiments with nitrogen as a seeding gas in fusion plasma devices, together with the decision to use beryllium as an armor material in the international fusion experiment ITER, have triggered interest in interactions of energetic N ions with Be and the influence of possible compound formation on parameters relevant to reactor operation and safety. Laboratory experiments are performed to investigate the properties of the ‘mixed material’ formed upon bombardment of bulk Be with energetic (keV) nitrogen ions. The formation of beryllium nitride within the implantation zone of a few nanometres is observed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Upon implantation of N at 1.5 keV per atom, saturation of the Be surface with N occurs at a fluence of 2 × 1018 N cm−2 and a retained areal density of approximately 4 × 1016 N cm−2. The nitride undergoes an ordering process upon annealing, but does not decompose at temperatures up to 1000 K. The influence of such nitride layers on the retention and release of D implanted with different fluences is investigated by nuclear reaction analysis and temperature-programmed desorption. The nitride layer does not act as a diffusion barrier for out-diffusing hydrogen isotopes. A partial sputter yield of 0.013 N/D as a lower limit is measured upon bombardment of the nitride layer with D at 2 keV. These erosion measurements are influenced by the strong tendency of the nitride to oxidize.

Ellipsometric study of a-Be 3N 2 thin films prepared by radio frequency magnetron sputtering

The ellipsometric characterizations of amorphous beryllium nitride (a-Be 3N 2) thin films deposited on Si (1 0 0) and quartz at temperature <50 °C using reactive RF sputtering deposition were examined in the wavelength range 280–1600 nm. X-ray diffraction of the films showed no structure, suggesting the Be 3N 2 films grown on the substrates are amorphous. The composition and chemical structures of the amorphous thin films were determined by using electron spectroscopy for chemical analysis. The surface morphology of a-Be 3N 2 was characterized by atomic force microscopy. The thicknesses and optical constants of the films were derived from spectroscopic ellipsometry measurements. The variation of the optical constants with thickness of the deposited films has been investigated. From the angle dependence of the polarized reflectivity we deduced a Brewster angle of 64°. At any angle of incidence, the a-Be 3N 2 shown high transmissivity (80–99%) and low reflectivity (<18%) in the visible and near infrared regions. Hence, the a-Be 3N 2 could be a good candidate for antireflection optical coatings under conditions of optimized the type of polarization and the angle of incidence.

Optical properties of sputtered amorphous beryllium nitride thin films

The optical properties of amorphous beryllium nitride (a-Be3N2) thin films deposited on Si (100) at temperature &amp;lt;50°C using reactive rf sputtering deposition were examined in the wavelength range of 280–1600nm. X-ray diffraction of the films showed no structure, suggesting the Be3N2 films grown on the Si (100) substrates are amorphous. The thicknesses and optical constants of the films were derived from variable-angle spectroscopic ellipsometry measurements using the Cauchy-Urbach model. Refractive indices and extinction coefficients of the films were determined to be in the range n=1.98–2.28 and κ=0.0002–0.08, respectively. Analysis of the absorption coefficient shows the optical absorption edge of a-Be3N2 films to be 4.12±0.01eV. These values were in excellent agreement with the photoluminescence measurements (4.18eV). The surface morphology was characterized by atomic force microscopy. The surfaces of the films were very smooth and their average roughnesses were measured to be in the range of 0.36–2.4nm. An effective medium approximation model of 50% Be3N2 and 50% voids was used in the ellipsometric fitting procedure. The spectral dependence of transmissivity of the films was investigated at different angles of incidence (20°–80°). The a-Be3N2 films shown high transmissivity (80%–99%) in the visible and near infrared regions.

Pulsed growth

Beryllium nitride thin films, candidates for optoelectronic applications, have been grown by pulsed laser deposition on silicon substrates. The films were prepared by ablating a beryllium foil in an N2 environment at several pressures and substrate temperatures. Real_time ellipsometric monitoring for the period of deposition was carried out in the 1.625 to 4.405 eV photon_energy range. The films were characterised in situ by electron spectroscopies and ex situ by AFM and SEM. A model for the growth of beryllium nitride was applied to reproduce the optical measurement and concurrently, the refractive index from the visible to the near ultraviolet spectral region was calculated. The estimated optical bandgap 4.0–4.2eV correlates closely with previously published theoretical results. This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.

Beryllium nitride: an alternative material to beryllium for extreme ultraviolet and soft X-ray uses

Extreme ultraviolet and soft X-ray optical systems require low absorbing materials for many technological applications. In this paper, the optical properties of beryllium nitride (Be 3 N 2 ) are studied and compared with those of beryllium (Be), a widely used material in this context. Thus, the dielectric function of Be and Be 3 N 2 are determined in the 4–100 eV energy interval by means of reflection electron energy loss spectroscopy. It is found that the absorption coefficient of Be and Be 3 N 2 are similar in the 40–100 eV energies range. Thereafter, the superior chemical stability and mechanical properties of Be 3 N 2 makes it a promising Be substitute as optical material in severe environments.

Ab initio calculations of the electronic and structural properties of beryllium-, magnesium- and calcium-nitrides

Abstract The electronic and structural properties of beryllium nitride (alpha and beta), magnesium- and calcium-nitrides were investigated using first principle full potential-linearized augmented plane wave method within density functional theory. We used Perdew and Wang-generalized gradient approximation, which is based on exchange correlation energy optimization, to calculate the total energy and the Engel–Vosko's GGA formalism, which optimize the corresponding potential, for band structure calculations. We also optimized internal parameters by relaxing the atomic positions in the force directions. Our results including lattice parameter, bulk modulus and it's pressure derivative, cohesive energy, band structure and density of states are compared with the experimental and other theoretical (Hartree–Fock approximation with a posteriori density functional correction) data.

Growth of beryllium nitride films by pulsed laser deposition; dielectric function determination

Beryllium nitride thin films, which are candidates for optoelectronic applications, have been grown by pulsed laser deposition on silicon substrates. The films were prepared by ablating a beryllium foil in N 2 environment at several pressures and substrate temperatures. Real-time ellipsometric monitoring for the period of deposition were carried out by a multiwavelength ellipsometer in the 1.625⩽ hν⩽4.405 eV photon-energy range. After its completion, the films were characterized in situ by electron spectroscopies and ex situ by atomic force and scanning electron microcopies. A model for the growth of beryllium nitride was applied to reproduce the optical measurement and concurrently, the refractive index from the visible to the near ultraviolet spectral region was calculated. The estimated optical bandgap correlates closely with previously published theoretical results.

Electronic and structural properties of β-Be 3N 2

We report the results of a theoretical study of the electronic and structural properties of the hexagonal beryllium nitride, using first principle pseudopotential plane wave (PP-PW) as well as full potential linearized augmented plane wave (FP-LAPW) methods within density functional theory. In the case of PP-PW we generated the pseudopotential by the highly optimized Q c-tuning method and used the local density approximation and generalized gradient approximation (GGA) for the exchange-correlation potential. We applied pressure on the unit cell by the Wentzcovitch and traditional methods. In the FP-LAPW approach only the GGA was used for the exchange-correlation potential. Our calculated values for structural properties, based on both approaches are in reasonable agreement with experimental and other theoretical (Hartree Fock) results. By applying the above two approaches and also the Tight Binding Linear Muffin Thin Orbital method, the ground state Kohn–Sham eigenvalues were calculated. The energy bands in three cases were similar and except for the energy gap values they were in good agreement with other theoretical results. Various versions of GGA functionals are usually obtained by optimizing the exchange correlation energy E XC rather than the corresponding potential V XC. As these functionals are not able to simultaneously reproduce E XC and V XC, hence they cannot obtain an accurate value for the band gap which mainly depends on the potential. Engel and Vosko (Phys. Rev. B 47 (1993) 13164) have proposed an alternate form of GGA which is based on optimizing V XC instead of the integral quantity E XC. We used this functional to calculate the band gap and the result seems to be more reasonable. Finally the total and partial densities of states were calculated for each atom.

Epitaxial α-Be 3N 2 thin films grown on Si substrates by reactive laser ablation

Beryllium nitride thin films were grown on (1 1 1) and (1 0 0) silicon substrates by laser ablating a beryllium foil in molecular nitrogen ambient from room temperature up to 900 °C. Resulting films were characterized using scanning and transmission electron microscopies, X-ray diffraction, Auger electron and X-ray photoelectron spectroscopies. Epitaxial films were achieved at substrate temperatures of 750 °C on (1 1 1)-Si. The diffraction measurements are in agreement with the α-Be 3N 2 phase. The orientation relationship between film-substrate corresponds to [1 1 0] Si [2 1 ̄ 0] Be 3 N 2 and (1 1 ̄ 1) Si ( 1 ̄ 2 ̄ 3) Be 3 N 2 .