Direct Band Gap Semiconductor Research Articles

MoSSe/Si9C15 heterojunction photodetectors with ultrahigh photocurrent and carrier mobility

The structural, electronic, optical properties and photogalvanic effect of MoSSe/Si9C15 and Si9C15/MoSSe heterostructures are investigated utilizing density functional theory. Band gaps of 1.70 eV and 1.03 eV are respectively exhibited by these heterostructures, both classified as direct bandgap semiconductors. The thermal stability of the MoSSe/Si9C15 and Si9C15/MoSSe heterostructures is demonstrated through ab initio molecular dynamics calculations. A hole mobility of 62774 cm2/Vs in the zigzag direction and an electron mobility of 1248 cm2/Vs in the armchair direction are recorded for the MoSSe/Si9C15 heterostructure. Light absorption in both the ultraviolet and visible light regions is observed for these heterostructures. Upon construction of a self-powered MoSSe/Si9C15 photodetector, a peak photocurrent (Jph) of 10.76 a02/photon is achieved, influenced by changes in polarization angle θ and photon energy, and a maximum extinction ratio of 26.7 is reached, showcasing high polarization sensitivity.

Effect of biaxial strain on the electronic structure and optical properties of two-dimensional Bi2Te2S

In this work, the effects of biaxial strain on the electronic structure and optical properties of monolayer Bi2Te2S are studied by the first-principles methods. The calculated results show that the monolayer Bi2Te2S is an indirect band gap semiconductor with a band gap of 1.0 eV. The absence of imaginary frequency in the phonon spectrum indicates that the structure can exist stably. With the increase of tensile strain, the band gap value decreases approximately quasi-linearly. When 10 % tensile strain is applied, the band gap value is reduced to 0 eV, achieving the transition from an indirect bandgap semiconductor to a direct bandgap semiconductor. With the increase of compressive strain, the band gap value increases first and then decreases, and the band gap value reaches a maximum of 1.28 eV at −4 % strain. Combined with the density of states analysis, the reason for this change in the band structure is that the contribution of Bi 6p, Te 5p and S 3p state electrons to the conduction band and valence band changes under different strains. The effect of strain on the optical properties shows that when different strains are applied, the monolayer Bi2Te2S has a high absorption coefficient in the entire visible region. The single-layer Bi2Te2S material has a smaller refractive index under tensile strain. The static dielectric function value increases with the increase of tensile strain, and the peak value of the dielectric function decreases and moves to the low energy direction. This indicates that the tensile strain will enhance the migration of photogenerated electron-hole pairs, which is beneficial to improving the utilization of light. This work will provide a theoretical reference for the subsequent study of the electronic and optical properties of monolayer Bi2Te2S.

A systematic first-principles investigation of the structural, electronic, mechanical, optical, and thermodynamic properties of Half-Heusler ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) for spintronics and optoelectronics applications.

This paper is the first to look at the structural, electronic, mechanical, optical, and thermodynamic properties of the ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) half-Heusler (HH) using DFT based first principles method. The lattice parameters that we have calculated are very similar to those obtained in prior investigations with theoretical and experimental data. The positive phonon dispersion curve confirm the dynamical stability of ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The electronic band structure and DOS confirmed that the studied materials ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) are direct band gap semiconductors. The investigation also determined significant constants, including dielectric function, absorption, conductivity, reflectivity, refractive index, and loss function. These optical observations unveiled our compounds potential utilization in various electronic and optoelectronic device applications. The elastic constants were used to fulfill the Born criteria, confirming the mechanical stability and ductility of the solids ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The calculated elastic modulus revealed that our studied compounds are elastically anisotropic. Moreover, ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) has a very low minimum thermal conductivity (Kmin), and a low Debye temperature (θD), which indicating their appropriateness for utilization in thermal barrier coating (TBC) applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are determined by calculations derived from the phonon density of states.

Unveiling the potential of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite as absorbent for photovoltaic application: first-principles insights into the structural, elastic, mechanical, electronic, thermodynamic and optical properties

This study explores the structural, elastic, mechanical, electronic, and optical properties of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite, a crucial material in photovoltaic cells. Utilizing type II-IV-V2 chalcopyrite, widely employed in high-efficiency solar cell production, we employ first-principles calculations with Tran–Blaha-modified Becke–Johnson exchange potential techniques. We aim to determine the band gap and optical properties to understand the compound’s morphology, crucial for solar cell development. Results show CuAlxGa1−xSe2 as a 1.36 eV direct band gap semiconductor. Optical characteristics, including dielectric tensor components and absorption coefficient, are calculated to assess its suitability for solar cell applications. Predictions of Young’s modulus E, Poisson’s ratio ν, bulk B, and shear G moduli provide insight into the crystal’s mechanical behavior. Additionally, phonon, dynamical stability, and thermodynamic properties are discussed, shedding light on the material’s potential in photovoltaic technology.

2D Janus TeMoZAZ’ (A = Si,Ge; Z,Z’ = N, P, As; Z ≠ Z'): First‐Principles Insight into the Electronics, and Piezoelectric Properties

AbstractJanus materials possess a diverse array of properties resulting from the breaking of mirror and inversion symmetries, holding significant potential for nanodevices. This study explores the novel TeMoZAZ' (A = Si,Ge; Z,Z' = N, P, As; Z ≠ Z') monolayers derived from the MoA2Z4 monolayer. Utilizing first‐principles calculations, the stability, electronic, transport, mechanical, and piezoelectric properties of the TeMoZAZ' monolayers are investigated. Among the 12 investigated structures, only five‐ TeMoNSiP, TeMoNSiAs, TeMoPSiAs, TeMoAsSiP and TeMoAsGeP monolayers‐ are found to be stable. The electronic properties analysis reveals metallic behavior in the TeMoNSiAs monolayer, while the remaining structures exhibit indirect or direct band gap semiconductor properties. Futher examination of the semiconducting monolayers indentifies the TeMoAsSiP monolayer with notably high hole carrier mobility along the y‐direction, reaching up to 3622.33 cm2 s−1 V−1. Moreover, investigation into the piezoelectric properties of these four semiconductor structures suggests their suitability for diverse applications in piezoelectric devices. Additionally, the effects of biaxial strain on the electronic and piezoelectric properties of these four semiconductor structures are explored. These findings propose a novel approach for designing 2D Janus materials, expanding the repertoire of 2D MA2Z4‐based Janus family and offering promising candidates for optoelectronic devices, wearable devices, and electromechanical systems.

The [100] direction strained Ge[formula omitted]Snx nanowires with low Sn contents towards the application of SWIR or MWIR lasers

The band structures of Ge1−xSnx nanowires with low Sn contents at the Γ-valley and L-valley under the [100] direction stress are studied via effective-mass theory, and we find that Ge0.95Sn0.05 and Ge0.92Sn0.08 nanowires can be tuned to direct-bandgap semiconductors even for the stress less than 4 GPa. Moreover, as increasing the stress, the calculations of the optical gain manifest that the z direction peak gain can be enhanced sharply regardless of the diameter and Sn content since more elelctrons are filled at the Γ-valley. The further research shows that the FCA loss of Ge1−xSnx nanowires can almost be neglected, meanwhile remarkable and positive net peak gain along the z direction can be acquired even though electron concentration is as low as the order of 1018 cm−3, which can overcome the non-negligible FCA loss caused by electron concentration of the order of 1019 cm−3 in Ge or strain-free Ge1−xSnx nanowires.

Structural and optoelectronic properties of Zn1-x-yBexMgyTe/InP quaternary alloys: A theoretical study

Density functional calculations show that designed zinc blende Zn1-x-yBexMgyTe/InP quaternary alloys are Γ-centered direct band-gap semiconductors and stable within a wide compositional range. Enhancement in the of Be and Mg compositions sum enhances lattice constant, but reduces minimum band-gap of these quaternary alloys. The Te-5p of valence to Zn-5s; Be-2p,3s; Mg-4s, 3p of conduction band HOMO-LUMO electronic excitations collectively control their optical properties. Such transitions show significant optical absorption in the ultra-violet (UV) region of the electromagnetic spectrum. Calculated optical energy-gaps of these alloys reside in the UV region. Optical energy-gap of quaternary alloy is found to be overestimated with respect to the corresponding fundamental band-gap. With enhancement in the Be and Mg compositions sum, both the fundamental band-gap and optical energy-gap exhibit blue-shift. Computed ε1 (0), n (0) and R (0) reduces with growing band-gap and vice versa. These Zn1-x-yBexMgyTe/InP semiconductor quaternary alloys with such optoelectronic features would be compatible for fabricating UV optoelectronic devices.

Modulated bandgap and gas adsorption behavior on two-dimensional SrAl2S4 monolayer: Potential applications for photovoltaic and energy storage

The structure of a novel two-dimensional layered material SrAl2S4 monolayer has been proposed, and its kinetic and thermodynamic stability has been confirmed. Researches have shown that SrAl2S4 monolayer is a semiconductor material with a bandgap of 1.630 eV for PBE and 2.798 eV for HSE06 at the ground state. Under biaxial strain, SrAl2S4 monolayer can complete the transition from a direct bandgap semiconductor to an indirect bandgap semiconductor, and its bandgap can vary between 0.187 eV and 1.712 eV. In addition, We have considered the adsorption behavior of SrAl2S4 monolayer for hydrogen and oxygen molecules, and the results show that SrAl2S4 monolayer adsorbed H2 molecules remains a direct bandgap semiconductor, whereas SrAl2S4 monolayer adsorbed O2 molecules show indirect bandgap semiconductor properties. At the same time, the adsorption of O2 molecules causes a flat band near the Fermi level, which increases the electrical conductivity. The few charges transfer observed between the SrAl2S4 monolayer and gas molecules confirms that the adsorption process of gas molecules on SrAl2S4 monolayer is physical adsorption. The tunable bandgap characteristics and good adsorption behavior of hydrogen and oxygen exhibited by SrAl2S4 monolayer make it a promising candidate material in the fields of photovoltaics and energy storage.

The structural, stability, electronic, optical and thermodynamic properties of Ba2AsXO6（X = V, Nb, Ta）double perovskite oxides: A First-Principles study

In this paper, the structural, mechanical, electronic, optical and thermodynamic properties of Ba2AsXO6 (X = V, Nb, Ta) double perovskite oxides have been studied based on the first principles of density functional theory. By calculating some parameters such as Goldsmith’s tolerance factor (tG), octahedral factor (µ), Bartel’s tolerance factor (τ), formation energy, binding energy and elastic constants, it is found that these double perovskite oxides have the potential for stable existence. In addition, Ba2AsXO6 (X = V, Nb, Ta) is an anisotropic material, in which Ba2AsVO6 is brittle, Ba2AsNbO6 and Ba2AsTaO6 are ductile. The electronic properties of the materials show that Ba2AsVO6 and Ba2AsNbO6 are indirect bandgap semiconductors with a band gap of 1.676 eV and 2.654 eV respectively, while Ba2AsTaO6 is direct bandgap semiconductor with a band gap of 3.252 eV. The optical properties revealed that these perovskites exhibit favorable far-ultraviolet light absorption characteristics. The thermodynamic properties show that the specific heat capacity of these double perovskite oxides reaches the Dulong-Petit limit at around 800 K. These results indicate that Ba2AsXO6 (X = V, Nb, Ta) double perovskite oxides have broad application prospects in the fields of thermoelectricity and optoelectronics. Furthermore, these results also provide a valuable theoretical basis for their future experimental synthesis.

Carrier Transport Properties of the Orthorhombic Phase Boron Nitride Nanoribbons and Rectifying Device Design

Using density functional theory combined with nonequilibrium Green's function, the electronic structures and carrier transport properties of the orthorhombic phase boron nitride nanoribbons (BNNRs) with different edges and different widths are investigated. The calculated results show that both armchair‐ and zigzag‐edged BNNRs are direct bandgap semiconductors. The quantum confinement gives rise to a distinct bandgap for the 1D BNNRs, and the edged atoms play an important role on their electronic structures. The bandgaps of the armchair‐edged BNNRs approach 0.5–0.8 eV when their widths are sufficiently large. However, the electronic structures of the zigzag‐edged BNNRs exhibit more variations dependent on their edged atoms. The J–V characteristics of the BNNRs reveal that the zigzag‐edged BNNRs have superior J–V performance to that of the armchair‐edged counterparts. Eventually, a computational nanodevice design is proposed to achieve rectifying behavior by constructing an in‐plane heterojunction based on the BNNRs without any doping, and the left and right electrodes are formed by differently edged atoms and a small strain is performed on the left electrode. The rectification ratio of about 77.36 is realized. The findings provide comprehensive understandings of the orthorhombic BN monolayer, which can be helpful to its potential application for nanoelectronics.

Strain engineering of electronic, mechanical, and optical properties of orthorhombic III–V group monolayers by first principles calculations

Using first principles calculations, we systematically investigated the effects of strain engineering on the electronic, mechanical, and optical properties of two-dimensional (2D) orthorhombic III–V group materials, including BN, BP, BAs, AlN, AlP, and GaN. It is shown that all the III–V orthorhombic monolayers exhibit excellent mechanical anisotropy for Young’s modulus, Shear modulus, and Poisson’s ratio, especially for the AlN and GaN monolayers. AlN, AlP, and GaN are predicted to be indirect bandgap semiconductors, with their bandgap of 0.70, 0.15, and 0.53 eV, respectively. And BN is demonstrated to be a direct bandgap semiconductor (0.63 eV). Under uniaxial tensile strains, their electronic structures have non-monotonic anisotropic variations and these monolayers can be effectively modulated from metal to semiconductor, experiencing indirect–direct bandgap transitions. In addition, all the orthorhombic III–V materials exhibit highly anisotropic light-harvesting performances and the optical absorbance can be efficiently tailored with tensile strains applied along a- and b-directions. The strong optical absorptions in the visible light regions suggested that AlN, BN, and GaN may be optically tunable 2D materials for component absorbance layers for solar cell applications. The excellent anisotropic and tunable electronic, mechanical, and optical performances indicate that the orthorhombic III–V monolayers are promising candidates for potential applications of optoelectronics and photovoltaics.

Effect of anion (S−2 & Se−2) replacement on photovoltaic properties in transition metal (Ba-Barium) chalcogenide perovskites

Material scientists have stepped up their search for efficient materials in low-cost, high-stability, nontoxic energy conversion devices. In this paper, emerging materials inspire us to study one of the perovskite chalcogens made from alkaline-earth metals (Barelium). Therefore, we determined some fundamental properties with some application-based properties, which explained their applicability in energy conversion device fabrication by first-principles calculation within the WIEN2K Code. Structure stability has been verified by Birch–Murnaghan fits and thermal stability at different temperatures and pressure ranges is explained by Gibbs function in thermodynamic properties. By using modified Becke–Johnson (mBJ) potential, electronic and optical characteristics of these materials provide insight into their nature: they were revealed to be direct bandgap semiconductors with the calculated values of 1.77[Formula: see text]eV (1.25[Formula: see text]eV) for BaZrS3(BaZrSe3), respectively. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. In the thermoelectric parameter, the figure of merit (ZT) is unity at room temperature and decreases up to 0.98 with temperature increment which reveals that these materials will be helpful in thermoelectric devices. As per the application part, we carried out the calculation of the spectroscopic limited maximum efficiency (SLME) and found that efficiency increases from 6.5% to 27.1% (8.1% to 31.9%) for BaZrS3 (BaZrSe3), respectively. The film thickness increased from 100[Formula: see text]nm to 1[Formula: see text][Formula: see text]m at room temperature and then stabilized. This emerging study shows that these materials can be used as an alert substance in energy conversion device fabrications and the proposed outcomes are in good acceptance with the experimental and other theoretical data. As per the optical and thermoelectric parameters of these materials, we infer that both are promising candidates in energy conversion device fabrication.

Double half Heusler (DHH) alloys with a high absorption coefficient shed light on the optoelectronic, thermoelectric, and structural, properties of X4Fe2Hf4Pt2 (X = Bi, Sb), derived from DFT data analysis

In this investigation, we employ density functional theory (DFT) with the generalised gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) and the modified Beck-Johnson approach (mBJ-GGA). Our focus is on examining the optoelectronic and thermoelectric properties of Bi4Fe2Hf4Pt2 and Sb4Fe2Hf4Pt2 compounds. The findings indicate that both compounds are stable in non-magnetic phase (NM). Regarding electronic characteristics, it is revealed that these compounds are direct bandgap semiconductors. The optical analysis suggests that these compounds demonstrate high reflectivity within the visible and ultraviolet spectra, rendering them promising candidates for solar cells and photovoltaic applications. Furthermore, these materials present as highly promising candidates for thermoelectric purposes due to their remarkable figure of merit (ZT) and notable Seebeck coefficient (S) values. However, there is a lack of theoretical or experimental data available for these compounds for conducting comparison with our results. We think future experimenters attempting to synthesise these chemicals experimentally will benefit from the current study.

Inserting intermolecular hydrogen bonds to achieve dimensional regulation and phase transition temperature enhancement

Organic-inorganic hybrid materials have become potential candidates in fields of light emitting diodes (LEDs), mechanical switches, energy conversion due to their excellent magneto-opto-electronic properties. Further improving the performance of materials is a prerequisite for achieving their commercial application. Currently, many effective strategies have been proposed and validated to enhance the properties of materials, but both simultaneously realizing the improvement phase transition temperature and dimensional regulation of materials remains a huge challenge. Here, we successfully synthesized two hybrid materials, (pyrrolidinium)PbI3 (Com-1) and (3-hydroxypyrrolium)6Pb5I16 (Com-2). In this work, the strategy of inserting intermolecular hydrogen bonds cleverly achieves a significant increase in phase transition temperature (ΔT = 81 K) and dimensional regulation (1D to 2D). Moreover, semiconductor properties of two compounds are investigated to be direct bandgap semiconductor. In short, inserting intermolecular hydrogen bonds between molecules is an effective strategy to improve physical performance.

Green synthesis and characterization of gold nanoparticles from discarded computer PCBs on reduction of environmental pollution

The economic value of gold content in electronic waste, particularly waste printed circuit boards (PCBs), has generated interest in recovering gold from this material. Unfortunately, due to the severe environmental hazards associated with such waste, there is a pressing need for efficient and selective methods of gold nanoparticle recovery. A novel technique has been developed to synthesize gold nanoparticles that employ chlorate leaching and Punica granatum extract to minimize the environmental impact of electronic waste. Multiple analytical methods, including UV-Vis, XRD, EDS, SEM, and TEM analysis, were utilized to identify and characterize the extracted gold nanoparticles. The UV-Vis spectrum showed GNP-absorption peaks at a narrow range of wavelengths, primarily at 520 nm, confirming the formation of gold nanoparticles from the e-waste. The XRD analysis identified the material as metallic gold with characteristic peaks of gold crystals (111), (200), (220), and (311), corresponding to the FCC crystal structure. The SEM and TEM analysis revealed that most of the Au nanoparticles were less than 40 nm in size, with some larger particles resulting from the agglomeration of smaller ones. The EDS spectrum analysis indicated that the gold atoms emitted strong signals. At the same time, other elements such as carbon, oxygen, and metals such as Sn, Zn, Pd, Cu, and Cd showed weaker signals. The recovered gold nanoparticles were found to have a bandgap of 2.2 eV, indicating that they are a direct bandgap semiconductor suitable for use in optoelectronic applications. The environmental impact of the PCBs and the chemicals used in the process were also analyzed to address the necessity of using discarded electronic waste to reduce environmental pollution. The proposed method showed high efficiency for extracting gold nanoparticles from e-waste, with simple process steps, low chemical usage, and low cost, as demonstrated by the results.

Tuning the Piezoelectric Performance of K0.5Na0.5NbO3 through Li Doping: Insights from Structural, Elastic and Electronic Analyses.

The structural, elastic, piezoelectric, and electronic properties of Li-doped K0.5Na0.5NbO3 (K0.5-xNa0.5-yLix+yNbO3, KNN-L) are calculated. The properties of KNN-L are related to the Li-doping content and the replaced K or Na atoms. The bulk modulus, the shear modulus, and Young's modulus of KNN-L are mostly higher than those of KNN, and the hardness value increases. The Poisson ratio of KNN-L is lower than that of most KNN, and the ductility is reduced. All doped structures are direct band gap semiconductors. K0.5Na0.375Li0.125NbO3 has the largest piezoelectric charge constant, d33 = 44.72 pC/N, in the respective structures, which is 1.5 fold that of K0.5Na0.5NbO3 (29.15 pC/N). The excellent piezoelectric performance of Li-doping KNN-L was analyzed from the insights of elastic and electronic properties.

DFT insights into the stoichiometric (001), (011) and (111) thin film surfaces of Ba2NaIO6

In this work, first-principles DFT calculations were performed to investigate the geometric, electronic, and magnetic properties of double perovskite Ba2NaIO6 (BNIO) in the bulk, and thin film form. The results showed that bulk BNIO in cubic phase (Fm-3m, #225) has a lattice constant of 8.43 Å, and is a non-magnetic direct band gap (Eg) semiconductor with Eg of 2.22 eV. Three types of cleaved surfaces namely (001), (011), and (111) oriented surfaces were considered here. The stability of the surfaces was examined with surface energy (Es). The Es is found to be 0.06, 0.09, 0.14 eV/Å2 respectively, for (001), (011), and (111) surface, indicating (001) as the energetically most favorable surface. All three surfaces exhibited metallic character, dominated by the splitting of O-p states of the top layer O-atoms. The (001) and (111) surfaces exhibited a magnetic character with magnetic moments of 0.1 and 2.23 μB per formula unit, whereas the (011) surface remained non-magnetic.

Physical properties and power conversion efficiency of SrZrX3 (X=S and Se) chalcogenide perovskite solar cell

The search for efficient substances in energy conversion devices, which are low-cost, highly stable, and not hazardous to humanity has intensified among material scientists. Here, we have investigated the chalcogenide-based metal (Sr — strontium) perovskites in the context of developing materials. We have identified the electrical and optical features of these materials using the modified Becke–Johnson potential, revealing information about their nature. With computed values of 2.009[Formula: see text]eV for SrZrS3 and 1.096[Formula: see text]eV for SrZrSe3, respectively, they have shown to be direct bandgap semiconductors. We have also found that both materials exhibit transparency to the striking photon at low energy and demonstrate absorption and optical conduction in the UV region. These materials will be useful in thermoelectric devices because the transport property calculation shows that their figure of merit is unity at both low and high temperatures. In regard to applications, we determined the spectroscopic limited maximum efficiency (SLME) of SrZrS3 (SrZrSe3) and discovered that the efficiency increases from 6.3% to 22.3% (7.9% to 32%) when the film thickness is increased from 100[Formula: see text]nm to 1[Formula: see text][Formula: see text]m at 300[Formula: see text]K, after that it stabilizes. This research shows that these materials ought to be utilized as an alert substance in the design of energy conversion products, and the proposed results are supported by experimental and other theoretical data. We suggest that these substances are strong contenders for use in power conversion equipment depending upon their optical and transport characteristics.

Unravelling the structural, electronic, mechanical and thermoelectric properties of half-Heusler alloys NaYX (X = C, Si, Ge, Sn)

We investigate the structural, electronic, and thermoelectric properties of the newly designed half-Heusler (hH) alloys NaYX (X = C, Si, Ge, Sn) using first-principles methods combined with Boltzmann transport theory. Our results indicate that the hH alloys are chemically, mechanically, as well as dynamically stable. The electronic calculations suggest that all the alloys are direct bandgap semiconductor with a bandgap of NaYC (0.52 eV), NaYSi (0.56 eV), NaYGe (0.57 eV) and NaYSn (0.65 eV). The lattice thermal conductivities of the hH alloys are quite low (12-24 W m−1 K−1) at room temperature. The computed figure of merit (ZT) for p-type charge carrier concentration show higher value for NaYC alloy (ZT = 0.57) as compared to NaYSi (ZT = 0.07),NaYGe (ZT = 0.27) and NaYSn (ZT = 0.42) at 1200 K, respectively. Altogether, our results indicate the potential of hH alloys for the high-temperature thermoelectric applications.

Electronic and optical properties of semiconducting BeN4 nanoribbons

Recently, a novel two-dimensional (2D) Dirac semimetal BeN4 have been successfully synthesized (Phys. Rev. Lett. 126, 175,501, 2021). However, the zero bandgap of monolayer BeN4 prevents it from performing as a semiconductor in next-generation optoelectronics and electronics. Here we employ first-principles calculations to show that cutting BeN4 monolayer along zigzag direction can open moderate band gaps. The zigzag BeN4 nanoribbons with Be termination are nonmagnetic (NM) semiconductors with a moderate direct band gap and good optical absorption. The nanoribbons with edges occupied by Be and N atoms are nonmagnetic semiconductors or ferromagnetic (FM)/NM metals, and the electronic properties are closely related to the type of boundary N atoms. The configuration with both edges occupied by the pentagonal N atoms is an antiferromagnetic (AFM) semiconductor, while the system with both edges situated by hexagonal N atoms is a NM direct band gap semiconductor. If one edge is terminated by hexagonal N atoms and the other one is pentagonal N atoms, the nanoribbon will behave as a FM semiconductor. We also explore the electronic properties of zigzag BeN4 nanoribbons with hydrogen passivation. These excellent properties endow zigzag BeN4 nanoribbons with enormous potential for applications in optoelectronic and spintronic devices.