A First‐Principles Study of C 3 N Nanostructures: Control and Engineering of the Electronic and Magnetic Properties of Nanosheets, Tubes and Ribbons

Recent Progress in Strain Engineering on Van der Waals 2D Materials: Tunable Electrical, Electrochemical, Magnetic, and Optical Properties

Strain engineering is a promising way to tune the electrical, electrochemical, magnetic, and optical properties of 2D materials, with the potential to achieve high-performance 2D-material-based devices ultimately. This review discusses the experimental and theoretical results from recent advances in the strain engineering of 2D materials. Some novel methods to induce strain are summarized and then the tunable electrical and optical/optoelectronic properties of 2D materials via strain engineering are highlighted, including particularly the previously less-discussed strain tuning of superconducting, magnetic, and electrochemical properties. Also, future perspectives of strain engineering are given for its potential applications in functional devices. The state of the survey presents the ever-increasing advantages and popularity of strain engineering for tuning properties of 2D materials. Suggestions and insights for further research and applications in optical, electronic, and spintronic devices are provided.

Recent Advances in the Spintronic Application of Carbon-Based Nanomaterials

The term "carbon-based spintronics" mostly refers to the spin applications in carbon materials such as graphene, fullerene, carbon nitride, and carbon nanotubes. Carbon-based spintronics and their devices have undergone extraordinary development recently. The causes of spin relaxation and the characteristics of spin transport in carbon materials, namely for graphene and carbon nanotubes, have been the subject of several theoretical and experimental studies. This article gives a summary of the present state of research and technological advancements for spintronic applications in carbon-based materials. We discuss the benefits and challenges of several spin-enabled, carbon-based applications. The advantages include the fact that they are significantly less volatile than charge-based electronics. The challenge is in being able to scale up to mass production.

Two-dimensional Dirac half-metal in porous carbon nitride C6N7monolayer via atomic doping

Motivated by the recent experimental discovery of C₆N₇monolayer (Zhaoet al2021Science Bulletin66, 1764), we show that C₆N₇monolayer co-doped with C atom is a Dirac half-metal by employing first-principle density functional theory calculations. The structural, mechanical, electronic and magnetic properties of the co-doped C₆N₇are investigated by both the PBE and HSE06 functionals. Pristine C₆N₇monolayer is a semiconductor with almost isotropic electronic dispersion around the Γ point. As the doping of the C₆N₇takes place, the substitution of an N atom with a C atom transforms the monolayer into a dilute magnetic semiconductor, with the spin-up channel showing a band gap of 2.3 eV, while the spin-down channel exhibits a semimetallic phase with multiple Dirac points. The thermodynamic stability of the system is also checked out via AIMD simulations, showing the monolayer to be free of distortion at 500 K. The emergence of Dirac half-metal in carbon nitride monolayer via atomic doping reveals an exciting material platform for designing novel nanoelectronics and spintronics devices.

Hypersonic impact properties of pristine and hybrid single and multi-layer C3N and BC3 nanosheets

Carbon, nitrogen, and boron nanostructures are promising ballistic protection materials due to their low density and excellent mechanical properties. In this study, the ballistic properties of C3N and BC3 nanosheets against hypersonic bullets with Mach numbers greater than 6 were studied. The critical perforation conditions, and thus, the intrinsic impact strength of these 2D materials were determined by simulating ballistic curves of C3N and BC3 monolayers. Furthermore, the energy absorption scaling law with different numbers of layers and interlayer spacing was investigated, for homogeneous or hybrid configurations (alternated stacking of C3N and the BC3). Besides, we created a hybrid sheet using van der Waals bonds between two adjacent sheets based on the hypervelocity impacts of fullerene (C60) molecules utilizing molecular dynamics simulation. As a result, since the higher bond energy between N-C compared to B-C, it was shown that C3N nanosheets have higher absorption energy than BC3. In contrast, in lower impact speeds and before penetration, single-layer sheets exhibited almost similar behavior. Our findings also reveal that in hybrid structures, the C3N layers will improve the ballistic properties of BC3. The energy absorption values with a variable number of layers and variable interlayer distance (X = 3.4 Å and 4X = 13.6 Å) are investigated, for homogeneous or hybrid configurations. These results provide a fundamental understanding of ultra-light multilayered armors' design using nanocomposites based on advanced 2D materials. The results can also be used to select and make 2D membranes and allotropes for DNA sequencing and filtration.

Investigation of strain and doping on the electronic properties of single layers of C6N6 and C6N8: a first principles study

In this work, by performing first-principles calculations, we explore the effects of various atom impurities on the electronic and magnetic properties of single layers of C6N6 and C6N8. Our results indicate that atom doping may significantly modify the electronic properties. Surprisingly, doping Cr into a holey site of C6N6 monolayer was found to exhibit a narrow band gap of 125 meV upon compression strain, considering the spin-orbit coupling effect. Also, a C atom doped in C6N8 monolayer shows semi-metal nature under compression strains larger than -2%. Our results propose that Mg or Ca doped into strained C6N6 may exhibit small band gaps in the range of 10-30 meV. In addition, a magnetic-to-nonmagnetic phase transition can occur under large tensile strains in the Ca doped C6N8 monolayer. Our results highlight the electronic properties and magnetism of C6N6 and C6N8 monolayers. Our results show that the electronic properties can be effectively modified by atom doping and mechanical strain, thereby offering new possibilities to tailor the electronic and magnetic properties of C6N6 and C6N8 carbon nitride monolayers.

Strain and electric field tuning of semi-metallic character WCrCO2MXenes with dual narrow band gap

Motivated by the recent successful synthesis of double-M carbides, we investigate structural and electronic properties of WCrC and WCrCO2monolayers and the effects of biaxial and out-of-plane strain and electric field using density functional theory. WCrC and WCrCO2monolayers are found to be dynamically stable. WCrC is metallic and WCrCO2display semi-metallic character with narrow band gap, which can be controlled by strain engineering and electric field. WCrCO2monolayer exhibits a dual band gap which is preserved in the presence of an electric field. The band gap of WCrCO2monolayer increases under uniaxial strain while it becomes metallic under tensile strain, resulting in an exotic 2D double semi-metallic behavior. Our results demonstrate that WCrCO2is a new platform for the study of novel physical properties in two-dimensional Dirac materials and which may provide new opportunities to realize high-speed low-dissipation devices.

Electronic properties and enhanced photocatalytic performance of van der Waals heterostructures of ZnO and Janus transition metal dichalcogenides

Vertical stacking of two-dimensional materials into layered van der Waals heterostructures has recently been considered as a promising candidate for photocatalytic and optoelectronic devices because it can combine the advantages of the individual 2D materials. Janus transition metal dichalcogenides (JTMDCs) have emerged as an appealing photocatalytic material due to the desirable electronic properties. Hence, in this work, we systematically investigate the geometric features, electronic properties, charge density difference, work function, band alignment and photocatalytic properties of ZnO-JTMDC heterostructures using first-principles calculations. Due to the different kinds of chalcogen atoms on both sides of JTMDC monolayers, two different possible stacking patterns of ZnO-JTMDC heterostructures have been constructed and considered. We find that all these stacking patterns of ZnO-JTMDC heterostructures are dynamically and energetically feasible. Moreover, both ZnO-MoSSe and ZnO-WSSe heterostructures are indirect band gap semiconductors and present type-I and type-II band alignments for model-I and model-II, respectively. The Rashba spin polarization of the ZnO-WSSe heterostructure for model-I is greater than that in the others. Furthermore, valence (conduction) band edge potentials are calculated to understand the photocatalytic behavior of these systems. Energetically favorable band edge positions in ZnO-Janus heterostructures make them suitable for water splitting at zero pH. We found that the ZnO-Janus heterostructures are promising candidates for water splitting with conduction and valence band edges positioned just outside of the redox interval.

Strain, electric-field and functionalization induced widely tunable electronic properties in MoS2/BC 3, /C 3 N and /[Formula: see text] van der Waals heterostructures

In this paper, the effect of BC ₃, C ₃ N and [Formula: see text] substrates on the atomic and electronic properties of MoS₂ were systematically investigated using first-principles calculations. Our results show that the MoS₂/BC ₃ and MoS₂/C ₃ N4 heterostructures are direct semiconductors with band gaps of 0.4 and 1.74 eV, respectively, while MoS₂/C ₃ N is a metal. Furthermore, the influence of strain and electric field on the electronic structure of these van der Waals heterostructures is investigated. The MoS₂/BC₃ heterostructure, for strains larger than -4%, transforms it into a metal where the metallic character is maintained for strains larger than -6%. The band gap decreases with increasing strain to 0.35 eV (at +2%), while for strain (>+6%) a direct-indirect band gap transition is predicted to occur. For the MoS₂/C₃N heterostructure, the metallic character persists for all strains considered. On applying an electric field, the electronic properties of MoS₂/C₃N₄ are modified and its band gap decreases as the electric field increases. Interestingly, the band gap reaches 30 meV at +0.8 V/Å, and with increase above +0.8 V/Å, a semiconductor-to-metal transition occurs. Furthermore, we investigated effects of semi- and full-hydrogenation of MoS₂/C₃N and we found that it leads to a metallic and semiconducting character, respectively.

Dirac half-metallicity of Thin PdCl3 Nanosheets: Investigation of the Effects of External Fields, Surface Adsorption and Defect Engineering on the Electronic and Magnetic Properties

PdCl₃ belongs to a novel class of Dirac materials with Dirac spin-gapless semiconducting characteristics. In this paper based, on first-principles calculations, we have systematically investigated the effect of adatom adsorption, vacancy defects, electric field, strain, edge states and layer thickness on the electronic and magnetic properties of PdCl₃ (palladium trichloride). Our results show that when spin-orbital coupling is included, PdCl₃ exhibits the quantum anomalous Hall effect with a non-trivial band gap of 24 meV. With increasing number of layers, from monolayer to bulk, a transition occurs from a Dirac half-metal to a ferromagnetic metal. On application of a perpendicular electrical field to bilayer PdCl₃, we find that the energy band gap decreases with increasing field. Uniaxial and biaxial strain, significantly modifies the electronic structure depending on the strain type and magnitude. Adsorption of adatom and topological defects have a dramatic effect on the electronic and magnetic properties of PdCl₃. In particular, the structure can become a metal (Na), half-metal (Be, Ca, Al, Ti, V, Cr, Fe and Cu with, respective, 0.72, 9.71, 7.14, 6.90, 9.71, 4.33 and 9.5 μ_B magnetic moments), ferromagnetic-metal (Sc, Mn and Co with 4.55, 7.93 and 2.0 μ_B), spin-glass semiconductor (Mg, Ni with 3.30 and 8.63 μ_B), and dilute-magnetic semiconductor (Li, K and Zn with 9.0, 9.0 and 5.80 μ_B magnetic moment, respectively). Single Pd and double Pd + Cl vacancies in PdCl₃ display dilute-magnetic semiconductor characteristics, while with a single Cl vacancy, the material becomes a half-metal. The calculated optical properties of PdCl₃ suggest it could be a good candidate for microelectronic and optoelectronics devices.

Control of C3N4 and C4N3 carbon nitride nanosheets’ electronic and magnetic properties through embedded atoms

In the present work, the effect of various embedded atom impurities on tuning electronic and magnetic properties of C₃N₄ and C₄N₃ nanosheets have been studied using first-principles calculations.

Embedding of atoms into the nanopore sites of the C6N6 and C6N8 porous carbon nitride monolayers with tunable electronic properties

Using first-principles calculations, we study the effect of embedding various atoms into the nanopore sites of both C₆N₆ and C₆N₈ monolayers.

Modulating the electro-optical properties of doped C3N monolayers and graphene bilayers via mechanical strain and pressure

The effect of atomic doping on the electronic properties of C₃N monolayer and graphene bilayer is investigated. We found that doped C₃N monolayer and doped graphene bilayer are a direct semiconductor. Our result show that the electronic properties of the studied structures can be modulated by electric field and mechanical strain.