Boron nitride (BN) is a structurally versatile insulator since it can be found in several crystalline structures with interesting mechanical and electrical properties, making this material attractive for technological applications. Seeking to improve its features, experimental and simulational studies for the amorphous phase (a-BN) have been carried out by some groups, focusing on the electrical and structural properties, pressure-induced phase transformations, and hydrogenated a-BN. In this work two amorphous structures are computationally generated and studied using ab initio Molecular Dynamics on a 216-atom supercell with two different densities, 2.04 and 2.80 g cm$^{-3}$. Our undermelt-quench approach is followed, since it has proven to give good structures for disordered materials and their properties. The topology, the vibrational density of states and some thermodynamic properties of the two samples are reported and compared with existing experiment. Some computational results are also revisited.
The effect of doping of cubic boron nitride with beryllium, silicon, sulfur and magnesium on the lattice parameters, electrical conductivity and EPR spectra has been studied. It is established that the degree of doping increases significantly in the case of crystallization of cubic boron nitride from BN solutions in supercritical ammonia at 3.9-4.2 GPa and 1100°C in comparison with the conventional synthesis from melts of the Mg-B-N system at 4.2 GPa and 1400°C. Doping with silicon and beryllium results in semiconductor properties of cubic boron nitride.
Nanostructure and mechanical properties of bulk nanocristalline cubic boron nitride have been studied by transmission electron microscopy, and micro- and nanoindentation. The obtained data on hardness, elastic properties and fracture toughness clearly indicate that nano-cBN belongs to a family of advanced ultra-hard materials.
Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4-trichlorobenzene. The product is imaged with high resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon-containing material is detected inside the boron nitride nanotubes with energy-dispersive x-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra.
Influence of Interface Geometry on Phase Stability and Bandgap Engineering in Boron Nitride substituted Graphene: A Combined First-principles and Monte Carlo Study
The defect-mediated hexagonal boron nitride (hBN) supercell display the visible optical spectra and electronic characteristics. The defects in the hBN supercell include the atomic vacancy, antisite, antisite vacancy, and substitution of a foreign atom for boron or nitrogen. The hBN supercell with VB, CB, and NB-VN has the high electron density of states across the Fermi level which indicates the high conductive electronic characteristics. The hBN with defects including atomic vacancy, antisite vacancy, and substitution of a foreign atom for boron or nitride exhibit the distinct spin-resolved o…
Length dependent lattice thermal conductivity of single \& multi layered hexagonal boron nitride: A first-principles study using the Callaway-Klemens \& real space super cell methods
Covalent functionalization is a way to tune the electrochemical properties of hexagonal boron nitride (h-BN) monolayers. The wide band gap insulator h-BN may become metallic conductor upon functionalization with strong oxidants, such as fluorosulfonyl radicals ($\cdot$OSO$_2$F), as known since 1978 [N. Bartlett et al., J. Chem. Soc. Chem. Comm. {\bf 5}, 200 (1978)], with electrical conductivity of 1.5 S/cm [C. Shen et al., J. Solid State Chem. {\bf 147}, 74 (1999)] that greatly surpasses commercial cathode material Li$_{x}$CoO$_{2}$ while retaining excellent ionic conductivity. Functionalized …
The current rechargeable battery technologies have a failure in their performance at high pressure and temperature. In this article, we have brought theoretical insights on using boron nitride flakes as a protecting layer for a lithium-ion battery device and extended its application for a spin-dependent photon emission device. Hence, the electronic properties of pristine and lithium-doped hydrogen-edged boron nitride flakes have been studied by the first principle density functional theory calculations. In this study, we have discussed the stability, adsorption energies, bond lengths, electron…
We present an ab-initio study of boron nitride as well as carbon allotropes. Their relative thermodynamic stabilities and structural phase transitions from low- to high-density phases are investigated. Pressure-temperature phase diagrams are calculated and compared to experimental findings. The calculations are performed using quantum chemical wavefunction based as well as density functional theories. Our findings reveal that predicted energy differences often depend significantly on the choice of the employed method. Comparison between calculated and experimental results allows for benchmarki…
Stacking and Registry Effects in Layered Materials: The Case of Hexagonal Boron Nitride
采用van der Waals修正的密度泛函理论方法研究了六方氮化硼（h-BN）的层间滑移能谱.结果表明，范德华力的主要作用是将层间固定在一个固定的距离上，而静电力则决定了最佳的堆积模式和层间滑动能。一个几乎自由滑动的路径被确定，沿着该路径获得~0.6 eV的带隙调制。我们提出了一个简单的几何模型，量化层之间的注册表匹配，并捕捉波纹h-BN层间能量景观的本质。这种现象学模型的简单性为复杂的层状结构（如碳和氮化硼纳米管）的建模开辟了道路。
Spin defects in foils of hexagonal boron nitride are an attractive platform for magnetic field imaging, since the probe can be placed in close proximity to the target. However, as a III-V material the electron spin coherence is limited by the nuclear spin environment, with spin echo coherence time of $\sim100~\mathrm{ns}$ at room temperature accessible magnetic fields. We use a strong continuous microwave drive with a modulation in order to stabilize a Rabi oscillation, extending the coherence time up to $\sim4~\mathrm{μs}$, which is close to the 10-$\mathrm{μs}$ electron spin lifetime in our …
The possibility of modification of the local properties of hexagonal boron nitride (h-BN) by laser irradiation is investigated. Investigations conducted using both Raman spectroscopy and electrostatic force microscopy were performed. Laser light induced modifications are found to cause no structural changes. However, they have impact on Raman spectra and local charge state of the material. They are also shown to be stable in time and during electrical grounding of the sample. The mechanism of photoionization of deep defects present in h-BN is proposed to explain the observed phenomenon. The di…
The structure of amorphous materials has been debated since the 1930's as a binary question: amorphous materials are either Zachariasen continuous random networks (Z-CRNs) or Z-CRNs containing crystallites. It was recently demonstrated, however, that amorphous diamond can be synthesized in either form. Here we address the question of the structure of single-atom-thick amorphous monolayers. We reanalyze the results of prior simulations for amorphous graphene and report kinetic Monte Carlo simulations based on alternative algorithms. We find that crystallite-containing Z-CRN is the favored struc…
Single layer hexagonal boron nitride is produced on 2 inch Pt(111)/sapphire wafers. The growth with borazine vapour deposition at process temperatures between 1000 and 1300 K is in-situ investigated by photoelectron yield measurements. The growth kinetics is slower at higher temperatures and follows a tanh$^2$ law which better fits for higher temperatures. The crystal-quality of h-BN/Pt(111) is inferred from scanning low energy electron diffraction (x-y LEED). The data indicate a strong dependence of the epitaxy on the growth temperature. The dominant structure is an aligned coincidence lattic…
Experimental study on the influence of binders on plastic deformation during sintering of cubic boron nitride powder under high pressure and high temperature
Hexagonal boron nitride (hBN) has been grown on sapphire substrates by ultra-high temperature molecular beam epitaxy (MBE). A wide range of substrate temperatures and boron fluxes have been explored, revealing that high crystalline quality hBN layers are grown at high substrate temperatures, $>$1600$^\circ$C, and low boron fluxes, $\sim1\times10^{-8}$ Torr beam equivalent pressure. \emph{In-situ} reflection high energy electron diffraction (RHEED) revealed the growth of hBN layers with $60^\circ$ rotational symmetry and the $[11\bar20]$ axis of hBN parallel to the $[1\bar100]$ axis of the sapp…
We present a first-principles computational study of the thermodynamics of carbon defects in hexagonal boron nitride (hBN). The defects considered are carbon monomers, dimers, trimers, and larger carbon clusters, as well as complexes of carbon with vacancies, antisites, and substitutional oxygen. Our calculations show that monomers ($\text{C}_{\text{B}}$, $\text{C}_{\text{B}}$), dimers, trimers, and $\text{C}_{\text{N}}\text{O}_{\text{N}}$ pairs are the most prevalent species under most growth conditions. Compared to these defects, larger carbon clusters, as well as complexes of carbon with va…
