本文采用密度泛函理论和局域密度近似，研究了尖晶石相（$γ$-M $_3$ N $_4$，M= C，Si，Ge和Sn）和$β$相（$β$ -M $_3$ N $_4$，M= Si，Ge和Sn）中的14族氮化物（M $_3$ N $_4$）.这些系统的Kohn-Sham能量首先在全势线性增广平面波的框架内计算，然后使用单发G $_0$ W $_0$计算进行校正，我们已经在Elk全势LAPW代码的修改版本中实现了该计算。已经发现尖晶石型氮化物$γ$ N $_4$（M= Si、Ge和Sn）在$Γ$点处的直接带隙。相应的GW校正的带隙与实验一致。我们还发现，GW计算与等离子体磁极近似和没有给出非常相似的结果，即使当系统包含半芯$d$电子。这些尖晶石型氮化物由于其直接和可调的带隙而成为潜在的光电应用的新型材料。
英文摘要：
We have investigated the group 14 nitrides (M$_3$N$_4$) in the spinel phase ($γ$-M$_3$N$_4$ with M= C, Si, Ge and Sn) and $β$ phase ($β$-M$_3$N$_4$ with M= Si, Ge and Sn) using density functional theory with the local density approximation and the GW approximation. The Kohn-Sham energies of these systems have been first calculated within the framework of full-potential linearized augmented plane waves and then corrected using single-shot G$_0$W$_0$ calculations, which we have implemented in the modified version of the Elk full-potential LAPW code. Direct band gaps at the $Γ$ point have been found for spinel-type nitrides $γ$-M$_3$N$_4$ with M= Si, Ge and Sn. The corresponding GW-corrected band gaps agree with experiment. We have also found that the GW calculations with and without the plasmon-pole approximation give very similar results, even when the system contains semi-core $d$ electrons. These spinel-type nitrides are novel materials for potential optoelectronic applications because of their direct and tunable band gaps.
We report on the synthesis of new nitride-based compound by using annealing of AlN heteroepitaxial layers under a Si-atmosphere at temperatures between 1350$^\circ$C and 1550$^\circ$C. The structure and stoichiometry of this compound are investigated by high-resolution scanning transmission electron microscopy (HRSTEM), energy dispersive X-Ray (EDX) spectroscopy, and density functional theory (DFT) calculations. The identified structure is a derivative of the parent wurtzite AlN crystal where anion sublattice is fully occupied by N atoms and the cation sublattice is the stacking of 2 different…
本报告从四面体键形成及其对价态密度的影响的角度，对氮化物化合物异常行为背后的机制提出了一致的见解。最近用于氧化的键带势垒（BBB）相关机制[Sun CQ，Prog Mater Sci 2003;48：521-685]扩展到氮化的电子过程，导致氮原子在与任意电负性较小的元素的固相中的原子相互作用时的sp轨道杂化的重要性。在氮化过程中，氮原子与周围的基质原子通过成键和非键相互作用形成准四面体，并产生电子空穴和反键偶极子，使基质的价带增加相应的态密度。结果表明，该体系的价态变化是其光致发光蓝移、冷阴极场发射功函数降低、耐腐蚀、耐磨损、高弹性和磁调制的主要原因。
We present improved band structure calculations of the Mg-IV-N$_2$ compounds in the quasiparticle self-consistent $GW$ approximation. Compared to previous calculations (Phys. Rev. B 94, 125201 (2016)) we here include the effects of the Ge-3$d$ and Sn-4$d$ semicore states and find that these tend to reduce the band gap significantly. This places the band gap of MgSnN$_2$ in the difficult to reach green region of the visible spectrum. The stability of the materials with respect to competing binary compounds is also evaluated and details of the valence band maximum manifold splitting and effectiv…
Rapid decline in fossil fuel energy necessitates the immediate need for renewable energy resources. Here, we report a previously unexplored class of nitrides AMN$_2$ keeping renewable energy applications in mind. Using a detailed structure and stability analysis using first principles simulation, we discovered twelve such compounds (few of which are already synthesized before), which are chemically, mechanically and dynamically stable. These twelve compounds were then evaluated for their suitability for three renewable energy applications, (i) photovoltaics, (ii) water splitting, and (iii) the…
The electronic band structures of BeSiN$_2$ and BeGeN$_2$ compounds are calculated using the quasiparticle self-consistent $GW$ method. The lattice parameters are calculated for the wurtzite based crystal structure commonly found in other II-IV-N$_2$ compounds with the $Pbn$2$_1$ space group. They are determined both in the local density approximation (LDA) and generalized gradient approximation (GGA), which provide lower and upper limits. At the GGA lattice constants, which gives lattice constants closer to the experimental ones, BeSiN$_2$ is found to have an indirect band gap of 6.88 eV and …
Binary III-N nitride semiconductors with wurtzite crystal structure such as GaN and AlN have been long used in many practical applications ranging from optoelectronic to telecommunication. The structurally related ZnGeN2 or ZnSnN2 derived from the parent binary compounds by cation mutation (elemental substitution) have recently attracted attention, but such ternary nitride materials are mostly limited to II-IV-N2 compositions. This paper reports on synthesis and characterization of zinc niobium nitride Zn2NbN3 - a previously unreported II2-V-N3 ternary nitride semiconductor. The Zn2NbN3 thin f…
We report $ab$ $initio$ band diagram and optical absorption spectra of hexagonal boron nitride ($h$-BN), focusing on unravelling how the completeness of basis set for $GW$ calculations and how electron-phonon interactions (EPIs) impact on them. The completeness of basis set, an issue which was seldom discussed in previous optical spectra calculations of $h$-BN, is found crucial in providing converged quasiparticle band gaps. In the comparison among three different codes, we demonstrate that by including high-energy local orbitals in the all-electron linearized augmented plane waves based $GW$ …
Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optoelectronic devices. In contrast, rocksalt-based nitrides are known for their metallic and refractory properties. Breaking this dichotomy, here we report on ternary nitride semiconductors with rocksalt crystal structures, remarkable optoelectronic properties, and the general chemical formula Mg$_{x}$TM$_{1-x}$N (TM=Ti, Zr, Hf, Nb). These compounds form over a broad metal composition range and our experiments show that Mg-rich compositions are nondegenerate semiconductors with visible-range optical abso…
We report a facile `metric' for the identification of structurally and dynamically (positive definite phonon structure) stable inorganic compounds. The metric considers charge-imbalance within the local substructures in crystalline compounds calculated using first-principles density-functional theory. To exemplify, we chose carbon-based nitrides as it provides a large pool of structurally stable and unstable phases. We showcase how local structural information related to Wyckoff symmetry uniquely identifies four new carbon-nitride phases. The metric predicts three new structurally stable phase…
Huge excitonic effects in layered hexagonal boron nitride
用全电子GW近似计算了块状六方氮化硼的准粒子能带结构，结果表明该化合物是一种间接带隙半导体。用电子-空穴双粒子格林函数的Bethe-Salpeter方程的解计算了它的光谱，结果与已有的实验数据符合得很好。对带隙内的激子结构进行了详细的分析，发现激子属于Frenkel类，并被紧紧地限制在层内。计算的激子结合能比Watanabe { \it et al}使用Wannier模型解释他们的实验结果并假设h-BN是直接带隙半导体得到的激子结合能大得多。
We propose a scheme to fabricate the cobalt nitride CoN4 monolayer, a magnetic graphene-like two-dimensional material, in which all Co and N atoms are in a plane. Under the pressure above 40 GPa, the bulk CoN4 is stabilized in a triclinic phase. With the pressure decreasing, the triclinic phase of CoN4 is transformed into an orthorhombic phase, and the latter is a layered compound with large interlayer spacing. At ambient condition, the weak interlayer couplings are so small that single CoN4 layer can be exfoliated by the mechanical method.
Manganese nitrides should be with amazing properties and promised application, because manganese atom is particular for its magnetism, valence states, high electron density, etc., and N atoms in compounds form different substructures. It is hard to good synthesize manganese nitride crystals with all established means, therefore, theoretical studies are highly welcome. In this study, we systematically examined the stoichiometric phases spaces of Mn-N compounds from 0 to 100 GPa based on ab initio calculations, and constructed the high pressure magnetic phase diagram. Remarkably, N-rich MnN4 wit…
Near-bandgap photoemission spectroscopy experiments were performed on p-GaN and p-InGaN/GaN photocathodes activated to negative electron affinity. The photoemission quantum yield of the InGaN samples drops by more than one order of magnitude when the temperature is decreased while it remains constant on the GaN sample. This indicates a freezing of photoelectron transport in p-InGaN that we attribute to electron localization in the fluctuating potential induced by the alloy disorder. This interpretation is confirmed by the disappearence at low temperature of the peak in the photoemission spectr…
Absorption and emission of pristine-like semiconducting monolayers of BN, AlN, GaN, and InN are here systematically studied by ab-initio methods. We calculate the absorption spectra for in-plane and out-of-plane light polarization including quasiparticle and excitonic effects. Chemical trends with the cation of the absorption edge and the exciton binding are discussed in terms of the band structures. Exciton binding energies and localization radii are explained within the Keldysh model for excitons in two dimensions. The strong excitonic effects are due to the interplay of low dimensionality, …
Four anti-perovskite-type compounds, ZnNNi3, ZnCNi3, SnNCo3, and SnCCo3, are synthesised through reactions between ingredient metal oxides and organic compound melamine (C3H6N6). ZnNNi3 and ZnCNi3 are selectively synthesised by choosing different reaction temperatures and nominal oxide-to-melamine ratios. SnNCo3 is synthesised for the first time by this melamine method. Resistivity, magnetisation, and heat capacity measurements reveal that SnNCo3 is a correlated metal with a high density of states at the Fermi level. Our results demonstrate that this feasible synthetic route using melamine is …
We report diffusion quantum Monte Carlo (DMC) and many-body $GW$ calculations of the electronic band gaps of monolayer and bulk hexagonal boron nitride (hBN). We find the monolayer band gap to be indirect. $GW$ predicts much smaller quasiparticle gaps at both the single-shot $G_0W_0$ and the partially self-consistent $GW_0$ levels. In contrast, solving the Bethe-Salpeter equation on top of the $GW_0$ calculation yields an exciton binding energy for the direct exciton at the $K$ point in close agreement with the DMC value. Vibrational renormalization of the electronic band gap is found to be si…
Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C$_3$N$_4$, nitrogenated holey grahpene C$_2$N, polyaniline C$_3$N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C$_9$N$_4$ stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C$_9$N$_4$ is found to be a 2D nodal-line semim…
Formation and protection of an Eu-Ir surface compound below hexagonal boron nitride
Centro de Física de Materiales (CSIC-UPV-EHU) and Materials Physics Center (MPC)（材料物理中心）；Departamento de Física Aplicada I, Universidad del País Vasco UPV/EHU（巴斯克大学应用物理学系）；Chalmers University of Technology（查尔姆斯理工大学）；Department of Physics, BITS Pilani, Hyderabad Campus（巴塔纳理工学院海德拉巴校区物理系）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）
Heterointerfaces have led to the discovery of novel electronic and magnetic states because of their strongly entangled electronic degrees of freedom. Single-phase chromium compounds always exhibit antiferromagnetism following the prediction of Goodenough-Kanamori rules. So far, exchange coupling between chromium ions via hetero-anions has not been explored and the associated quantum states is unknown. Here we report the successful epitaxial synthesis and characterizations of chromium oxide (Cr2O3)-chromium nitride (CrN) superlattices. Room-temperature ferromagnetic spin ordering is achieved at…
We report the design, synthesis, structure, and properties of two complex layered phosphide nitrides, $Ak$Th$_2$Mn$_4$P$_4$N$_2$ ($Ak$ = Rb, Cs), which contain anti-fluorite-type [Mn$_2$P$_2$] bilayers separated by fluorite-type [Th2N2] layers as a result of the intergrowth between AkMn$_2$P$_2$ and ThMnPN. The new compounds are featured with an intrinsic hole doping associated with the interlayer charge transfer and a built-in chemical pressure from the [Th$_2$N$_2$] layers, both of which are reflected by the changes in the lattice and the atomic position of phosphorus. The measurements of ma…
High-pressure x-ray diffraction and ab initio study of Ni2Mo3N, Pd2Mo3N, Pt2Mo3N, Co3Mo3N, and Fe3Mo3N: Two families of ultra-incompressible bimetallic interstitial nitrides
本文用高压X射线衍射研究了Ni_2 Mo_3 N、Co_3 Mo_3 N和Fe_3 Mo_3 N的结构稳定性。我们还报告从头计算这些化合物，Pd 2 Mo 3 N和Pt 2 Mo 3 N的高压性能的建模。我们已经发现，氮化物保持稳定的环境压力立方结构至少高达50 GPa，并确定其状态方程。它们都具有大于300 GPa的体积模量。单晶弹性常数已被计算，以量化的刚度的研究氮化物。我们发现它们应该具有与立方尖晶石氮化物如γ-Si 3 N4类似的维氏硬度
Non-metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. This characteristic relies on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly intriguing. In this study, the phosphorus-nitrogen system was studied up to 137 GPa in laser-heated diamond anvil cells and three previously unobserved phases were synthesized and characterized by single-crystal X-ray diffraction, Raman spectroscopy measurements and density functional theory calculations. Delta…
Motivated by the ongoing interest in nitrides as materials for spintronics applications we have studied effects of doping with magnetic transition-metal elements (T=Cr,Mn,Fe,Co and Ni) on the electronic properties of semiconducting scandium nitride. Using density functional together with the generalized gradient approximation (GGA) as well as PBE0r hybrid functional (with different mixing of the exact exchange), two different doping amounts 25\% ($\rm Sc_{0.75}T_{0.25}N$) and 10\% ($\rm Sc_{0.9}T_{0.1}N$) have been investigated. This is done in comparison to the reference compound ScN with a s…
Zinc-based nitride CaZn2N2 films grown by molecular beam epitaxy (MBE) with a plasma-assisted active nitrogen-radical source are promising candidates of next-generation semiconductors for light-emitting diodes and solar cells. This nitride compound has previously only been synthesized in a bulk form by ultrahigh-pressure synthesis at 5 GPa. Three key factors have been found to enable heteroepitaxial film growth: (i) precise tuning of the individual flux rates of Ca and Zn, (ii) the use of GaN template layers on sapphire c-plane as substrates, and (iii) the application of MBE with an active N-r…
A theoretical study of the exciton binding energy in the two-dimensional hexagonal boron nitride monolayer is presented within the tight-binding approximation (TBA). A self-consistent equation for the interband electron-hole propagators is derived and in the long wavelength limit reduced to the standard hydrogen atom like Schrodinger equation. It is shown that inclusion of dynamically screened Coulomb interaction in ladder term is of crucial importance for proper description of exciton binding energy. This leads to the self-consistent eigenvalue problem with dynamical screening. The dependence…
We present quasiparticle (QP) energies from fully self-consistent $GW$ (sc$GW$) calculations for a set of prototypical semiconductors and insulators within the framework of the projector-augmented wave methodology. To obtain converged results, both finite basis-set corrections and $k$-point corrections are included, and a simple procedure is suggested to deal with the singularity of the Coulomb kernel in the long-wavelength limit, the so called head correction. It is shown that the inclusion of the head corrections in the sc$GW$ calculations is critical to obtain accurate QP energies with a re…
