Si Vacancies Research Articles

Thermodynamic and kinetic controls on phase stability and incorporation of water in larnite (β-Ca2SiO4): implications for calcium silicate inclusions in diamonds

Larnite (β-Ca2SiO4) has previously been reported as an inclusion in sub-lithospheric diamonds and is generally interpreted as a retrograde reaction product of calcium silicate perovskite. In this study, we review the controls on the stability of the Ca2SiO4 polymorphs and show that phosphorus is likely essential for the preservation of β-Ca2SiO4. We also report a detailed study of the solubility of water and its incorporation mechanisms in γ-Ca2SiO4 and phosphorus-doped β-Ca2SiO4 using FTIR spectroscopy on high-pressure experiments quenched from 4–9.5 GPa and 1000–1200 °C combined with ab initio calculations. The experimentally determined water solubilities are in the range of 107–178 ppm. Our FTIR spectra and ab initio calculations indicate that for phosphorus-free γ-Ca2SiO4 the incorporation mechanism involves protonated Si and Ca1 vacancies. For phosphorus-bearing β-Ca2SiO4, our preferred incorporation mechanism involves one Si4+ ion replaced by one P5+ ion with a single protonated Ca2 vacancy. The low water solubility observed here for larnite implies that if primary calcium silicate perovskite inclusions trap high water concentrations during diamond growth from a volatile-rich fluid, measurements of the concentration of water in larnite will not provide a useful record of the initial volatile concentration. Instead, water would be hosted in other retrograde reaction products, possibly including exsolved fluids.

[formula omitted] magnetism engineering in the low-buckled hexagonal SiS monolayer: A first-principles study

In this work, vacancy- and doped-induced magnetism engineering is investigated to functionalize the non-magnetic low-buckled hexagonal silicon sulfide (SiS) monolayer. This monolayer is an indirect gap semiconductor two-dimensional (2D) material with an energy gap of 2.20(3.02) eV obtained from the PBE(HSE06)-based calculations. Creating a single Si vacancy leads to a significant magnetization of SiS monolayer with the feature-rich half-metallic nature. Herein, a total magnetic moment of 1.89 μB is obtained and magnetic properties are produced mainly by S and Si atoms closest to the defect site. In contrast, single S vacancy preserves the non-magnetic nature inducing a band gap reduction of the order of 26.36%. n-type doping with P atom metalizes the monolayer, meanwhile As impurity leads to the emergence of the half-metallicity with a total magnetic moment of 1.00 μB. Similarly, this value is also obtained by p-doping using P and As atoms as dopants, where the diluted magnetic semiconductor nature is obtained. Moreover, doping with IA- (Na and K) and IIIA-group (Al and Ga) atoms is also proposed to engineer the magnetism in SiS monolayer. It is found that these impurities induce either half-metallic or diluted magnetic semiconductor behaviors with total magnetic moment between 0.99 and 1.00 μB. The electronic and magnetic properties are regulated mainly by the interactions between impurities and their neighbor S atoms, which modify the charge distribution in their outermost orbitals. In addition, the Bader charge analysis asserts that dopant atoms gain charge from the host monolayer when substituting S atom, meanwhile they act as charge loser — transferring charge to the host monolayer when doping at Si sublattice. The presented results may suggest efficient approaches to properly engineer SiS monolayer electronic and magnetic properties, making new 2D candidates for spintronic applications.

Damage microstructures in Ti3SiC2 under successive Xe-He-H ions irradiation and annealing process

Ti3SiC2 is recognized as a promising candidate material for nuclear energy applications; however, the microstructural defects resulting from complex irradiation processes remain elusive. This study investigates the microstructural evolution of Ti3SiC2 under sequential Xe-He-H ions irradiation at room temperature, followed by annealing at 900 °C, employing both experimental and first-principles computational approaches. A reverse phase transformation occurred following He irradiation, indicating that He facilitates the remote migration and recombination of Si vacancies through the formation of He-Si pairs during annealing. Post-annealing, the Xe-irradiated sample exhibited a widespread distribution of small Xe bubbles, whereas larger bubbles were prevalent at peak damage regions in the samples subjected to Xe+He and Xe+He+H irradiation. Concurrently, Si-rich precipitates with distinct distribution patterns were observed in samples irradiated with Xe, Xe+He, and Xe+He+H ions, significantly affecting the hardness. First-principles calculations reveal that the distinct damage profiles are primarily attributed to the dynamic behaviors of Si interstitials. The Ti-Si bonds are relatively weak and easily broken, leading to abundant Si interstitials in Xe ion irradiation, and He enhances Si diffusion. Conversely, H enhances Si segregation by preventing He from capturing Si interstitials. Within the TiC grains, He promotes Si migration, causing an approximately 700-fold increase in Si diffusivity at 900 °C. The Si segregation leads to the nucleation of 〈110〉 dislocation loops, culminating in the formation of distinctive strip-like Si clusters. This study elucidates the formation mechanism of Si segregation within Ti3SiC2, providing valuable insights for the design of irradiation-resistant materials.

Understanding noble gas incorporation in mantle minerals: an atomistic study

Ab initio calculations in forsterite (Mg2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}SiO4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}) are used to gain insight into the formation of point defects and incorporation of noble gases. We calculate the enthalpies of incorporation both at pre-existing vacancies in symmetrically non-equivalent sites, and at interstitial positions. At high pressure, most structural changes affect the MgO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{6}$$\\end{document} units and the enthalpies of point defects increase, with those involving Mg and Si vacancies increasing more than those involving O sites. At 15 GPa Si vacancies and Mg interstitials have become the predominant intrinsic defects. We use these calculated enthalpies to estimate the total uptake of noble gases into the bulk crystal as a function of temperature and pressure both in the presence and absence of other heterovalent trace elements. For He and Ne our calculated solubilities point to atoms occupying mainly interstitial sites in agreement with previous experimental work. In contrast, Ar most likely substitutes for Mg due to its larger size and the deformation it causes within the crystal. Incorporation energies, as well as atomic distances suggest that the incorporation mainly depend on the size mismatch between host and guest atoms. Polarization effects arising from the polarizability of the noble gas atom or the presence of charged defects are minimal and do not contribute significantly to the uptake. Finally, the discrepancies between our results and recent experiments suggest that there are other incorporation mechanisms such as adsorption at internal and external interfaces, voids and grain boundaries which must play a major role in noble gas storage and solubility.

Dually functional NiSi intermetallic compounds for the efficient hydrogenation and oxidation of cinnamaldehyde

Intermetallic compounds (IMCs) are promising catalysts for upgrading biomass-derived platform chemicals. Herein, bifunctional NiSi IMCs catalysts were developed for the hydrogenation and oxidation of cinnamaldehyde (CAL). A solvent-free arc-melting method was employed for the synthesis of NiSi IMCs within 5 min. The NiSi IMCs catalysts afforded 99 % conversion of CAL and presented ∼ 71 % yield of 2-phenyl propanol and ∼ 34 % yield of benzaldehyde for the hydrogenation and base-free oxidation of CAL, respectively. Moreover, NiSi IMCs could be used for five runs without deactivation. Characterizations and theoretical calculation results indicated the formation of intermetallic structure and the existence of Si vacancy sites, which could not only facilitate the efficient hydrogenation of CAL but also expose NiOx species as catalytic centers for the oxidation of CAL, leading to the high performance and stability in both hydrogenation and oxidation process.

Point Defects in Hexagonal SiP Monolayer: A Systematic Investigation on the Electronic and Magnetic Properties

AbstractIn this work, point defects are proposed to modify the electronic and magnetic properties of SiP monolayer. Pristine monolayer is a non‐magnetic semiconductor 2D material with energy gap of 1.52(2.21) eV as predicted by PBE(HSE06) functional. Single Si vacancy (), Si+P divacancy (), and substituting one P atom by one Si atom () magnetize significantly SiP monolayer. Herein, total magnetic moments between 1.00 and 2.00 are obtained . In contrast, no magnetism is induced by single P vacancy (), substituting one Si atom by one P atom (), and exchanging pair Si‐P positions (). Moreover, significant magnetization of SiP monolayer is also achieved by doping with single Li and Cu atoms ( and ), as well as pair of Li and Cu atoms ( and ). Total magnetic moments between 0.84 and 1.42 are obtained. Interestingly, the half‐metallicity is observed in and systems. When substituting P atom, F, Cl, and Br impurities reduce significantly the SiP monolayer bandgap, preserving its non‐magnetic nature. In contrast, a total magnetic moment of 1.26 is obtained by doping with I atom. Results presented herein may introduce the defected and doped SiP systems as prospective 2D candidates for spintronic and optoelectronic applications.

The behaviors of He atoms at Ti3SiC2(001)/V(110) interface: A first-principles study

Ti3SiC2 nano-particles and He atom play an important role for the degradation of properties in vanadium alloys under irradiation environment. Herein, the behaviors of He atoms at C-Ti2-H Ti3SiC2(001)/V(110) interface model by first-principles calculations, which is the most thermodynamically stable, is studied to elucidate the effect of Ti3SiC2 nano-particles on the He bubble formation in the vanadium alloys. He atom tends to dissolve at the Ti3SiC2/V interface and at the near Si layer of Ti3SiC2 side at the interface. The vacancy type defects formation energies for V1, C1, C2 and Si, which both lower than V monovacancy formation energy in bulk vanadium, are more likely to form at the interface. Moreover, The existence of monovacancy at the interface makes it easier for neighboring He atoms to dissolve, which has a spatial effect on He atom. The result of the trapping energy and the interface distortion of He atom trapped by Si and V1 vacancies, more He atoms can be trapped as the number of vacancies increases. The diffusion of He atom located at Ti3SiC2 side towards the interface hampered by the small spacing Ti and C atom layers (dlsTi2−C2= 1.18 Å) anddlsTi1−C1 = 1.31 Å) He atom tends to aggerate at the interface due to the higher energy barrier. The Ti3SiC2-praticle/V-matrix interface can act as a sink for He atom. These findings provide a new insight into the understanding about the influence of Ti3SiC2 nano-particles on the mechanisms of He bubble formation and the guidance for further the preparation of vanadium alloys.

Ultrathick MA2N4(M'N) Intercalated Monolayers with Sublayer‐Protected Fermi Surface Conduction States: Interconnect and Metal Contact Applications

AbstractRecent discovery of ultrathick MoSi2N4(MoN)n monolayers open up an exciting platform to engineer two‐dimensional (2D) material properties via intercalation architecture. In this study, a series of ultrathick MA2N4(M'N) monolayers (M, M' = Mo, W; A = Si, Ge) is computationally investigated under both homolayer and heterolayer intercalation architectures, in which the same and different species of transition metal nitride inner core sublayer are intercalated by outer passivating nitride sublayers, respectively. The MA2N4(M'N) are stable metallic monolayers with excellent mechanical strength. Intriguingly, the metallic states around Fermi level are localized within the inner core sublayer. Carrier conduction mediated by electronic states around the Fermi level is thus spatially insulated from the external environment by the native outer nitride sublayers, suggesting the potential of MA2N4(M'N) in back‐end‐of‐line metal interconnect applications. N and Si (or Ge) vacancy defects at the outer sublayers create ‘punch through’ states around the Fermi level that bridges the carrier conduction in the inner core sublayer and the outer environment, forming an electrical contact akin to the ‘via' structures of metal interconnects. It is further shown that MoSi2N4(MoN) can serve as a quasi‐Ohmic contact to 2D WSe2. These findings reveal the potential of ultrathick MA2N4(MN) monolayers in interconnect and metal contact applications.

Variations in proton transfer pathways and energetics on pristine and defect-rich quartz surfaces in water: Insights into the bimodal acidities of quartz

HypothesisUnderstanding the mechanisms of proton transfer on quartz surfaces in water is critical for a range of processes in geochemical, environmental, and materials sciences. The wide range of surface acidities (>9 pKa units) found on the ubiquitous mineral quartz is caused by the structural variations of surface silanol groups. Molecular scale simulations provide essential tools for elucidating the origin of site-specific surface acidities. SimulationsWe used density-functional tight-binding-based molecular dynamics combined with rare-event metadynamics simulations to probe the mechanisms of deprotonation reactions from ten representative surface silanol groups found on both pristine and defect-rich quartz (101) surfaces with Si vacancies. FindingsThe results show that deprotonation is a highly dynamic process where both the surface hydroxyls and bridging oxygen atoms serve as the proton acceptors, in addition to water. Deprotonation of embedded silanols through intrasurface proton transfer exhibited lower pKa values with less H-bond participation and higher energy barriers, suggesting a new mechanism to explain the bimodal acidity observed on quartz surface. Defect sites, recently shown to comprise a significant portion of the quartz (101) surface, diversify the coordination and local H-bonding environments of the surface silanols, changing both the deprotonation pathways and energetics, leading to a wider range of pKa values (2.4 to 11.5) than that observed on pristine quartz surface (10.4 and 12.1).

Carrier injection induced degradation of nitrogen passivated SiC–SiO2 interface simulated by time-dependent density functional theory

The performance of SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) degrades seriously after a period of continuous operation. To directly understand this issue, we conduct real-time time-dependent density functional theory (TDDFT) simulations on a series of nitrogen passivated SiC–SiO2 interfaces to monitor the interaction between carriers and interface atoms. We find that the nitrogen passivation always leaves behind two local states near the VBM, which gives a chance to the strong interaction between channel carriers and C–N bonds, and finally results in the generation of C dangling bond defects. These processes are vividly presented and confirmed by the TDDFT simulation. Additionally, the results show that the new defects are more easily formed by the passivated C cluster than the passivated Si vacancy. These studies provide physical insights into the degradation mechanisms of working SiC MOSFETs, while simultaneously demonstrating the advantage of TDDFT as a crucial tool for investigating defect generation dynamics in semiconductor devices.

Effect of fission defects on tensile strength of U3Si2 Σ5(210) grain boundary from first-principles calculations.

U3Si2 is regarded as a promising accident tolerant fuel (ATF) to replace the commercial fuel UO2; however, grain boundary (GB) embrittlement of U3Si2 caused by irradiation-induced defect segregation remains to be clarified. In this work, the U3Si2 Σ5(210) symmetrically tilted GB is taken as a representative to elucidate the individual effect of xenon (Xe) and vacancy on the tensile strength and failure of GBs using first-principles calculations. Compared with the predicted segregation energies of defects at the most energetically favourable positions of GBs, Si vacancy (VSi) has a much stronger preference to segregate to GBs than that of Xe substitution on the Si sublattice (XeSi). Moreover, the strengthening/embrittlement potency of GBs with single vacancy/Xe is evaluated using the first-principles-based uniaxial tensile test. Although both VSi and XeSi yield a weakening effect on the strength of the U3Si2 Σ5(210) GB, such defective GBs exhibit significantly stronger interface strengths compared to the corresponding defects segregated to the UO2 Σ3(111) GB. The underlying mechanism of strength change of U3Si2 GBs is discussed in terms of charge analysis. Our results can provide a fundamental understanding of the mechanical behavior of irradiated GBs from an atomic perspective.

A DFT study on the effect of lattice defects on the electronic structures and floatability of spodumene

The influences of lattice vacancies and lattice impurities on the electronic structures and floatability of spodumene were studied by the density functional theory (DFT) through analysis of partial density of states (DOS), Mulliken population, differential charge density, and frontier molecular orbitals. The calculation indicated that the effect of lattice Al, Si, and Li vacancies on the DOS, Mulliken population as well as the interaction between spodumene and oleate was insignificant. Cr, Fe, and Mn impurities caused the shift of Fermi level towards lower energy and the occurrence of peaks of impurity near Fermi level. K and Na impurities contributed little to the lowest unoccupied molecular orbital (LUMO) of spodumene, while Cr, Fe, and Mn impurities had great contribution, suggesting that Cr, Fe, and Mn impurities significantly affected the interaction between spodumene and oleate. The frontier molecular orbitals analysis indicated Cr, Fe, and Mn impurities are in favor of oleate adsorption.

Defect effects on the electronic, valley, and magnetic properties of the two-dimensional ferrovalley material VSi2N4.

Due to their novel spin and valley properties, two-dimensional (2D) ferrovalley materials are expected to be promising candidates for next-generation spintronic and valleytronic devices. However, they are subject to various defects in practical applications. Therefore, the electronic, valley, and magnetic properties may be modified in the presence of the defects. In this work, utilizing first-principles calculations, we systematically studied the effects of defects on the electronic, valley, and magnetic properties of the 2D ferrovalley material VSi2N4. It has been found that C doping, O doping, and N vacancies result in the half-metallic feature, Si vacancies result in the metallic feature, and V vacancies result in a bipolar gapless semiconductor. These defect-induced electronic properties can be effectively tuned by changing defect concentration and layer thickness. Since the impurity bands do not affect the K and K' valleys, valley polarization is well maintained in O-doped and N-defective systems. Importantly, these defects play a crucial role in modifying the magnetic properties of the pristine VSi2N4, especially the magnitude of local magnetic moments and the magnetic anisotropy energy. Detailed analysis of the density of states demonstrates that the variations of the total magnetic moment and magnetic anisotropy energy with biaxial strain are determined by the electronic states near the Fermi level rather than the type of defect, which provides a new understanding of the effects of defects on the magnetic properties of 2D materials. Moreover, the layer thickness can affect the magnetic coupling between defects and surrounding V atoms. Our results offer insight into the electronic, valley, and magnetic properties of VSi2N4 in the presence of various point defects.

Identification of Optically Active Quartet Spin Centers Based on a Si Vacancy in SiC Promising for Quantum Technologies

Optically active (bright) and optically inactive (dark) quartet S = 3/2 spin color centers including a negatively charged Si vacancy have been identified in silicon carbide using high-frequency electron nuclear double resonance on the nuclei of the 13C isotope, enhanced by a tenfold increase in its content. The alignment of populations of spin levels is optically induced in a bright center promising for quantum technologies, whereas the populations of spin levels in a dark center, which is an isolated negatively charged Si vacancy V-Si, correspond to a Boltzmann distribution and do not change under optical excitation.

Density functional theory analysis of the sensitivity of silicene/graphene heterostructures toward HCN

This study investigated the adsorption behavior of HCN molecules on pristine, vacancy-induced defects, and transition-metal doped silicene/graphene heterostructures based on density functional theory. The HCN molecules exhibited physical adsorption on pristine silicene/graphene substrates. Introducing Si vacancies did not enhance the activity of silicene/graphene heterostructures, and the HCN molecules continued exhibiting physical adsorption. By contrast, the presence of dopant atoms (Sc, Ti, V, Cr, Mn, Co) enhanced the adsorption stability of HCN molecules. The adsorption of HCN on Ti-doped silicene/graphene heterostructures was the highest, and the results of the partial density of states indicated obvious hybridization between d orbitals of Ti and the p orbitals of HCN molecule. Sc-doped heterostructures exhibited shortest desorption time, suggesting it was suitable as reused sensors for detecting HCN. The obtained results provide new approach for the development of highly sensitive gas sensors based on heterostructures.

Identification of Optically Active Quartet Spin Centers Based on a Si Vacancy in SiC Promising for Quantum Technologies

Identification of Optically Active Quartet Spin Centers Based on a Si Vacancy in SiC Promising for Quantum Technologies

Mechanical properties of defective kaolinite in tension and compression: A molecular dynamics study

Influenced by the external environment, clays often contain a large number of lattice defects inside, and the defects have an essential influence on the physical and mechanical properties of clays. In order to reveal the mechanical properties and deformation failure mechanism of defective kaolinite, kaolinite containing Si vacancy defects was constructed, and the mechanical properties of two types of perfect/defective kaolinite were investigated under uniaxial tensile and compressive conditions, respectively, by using molecular dynamics methods. The anisotropy of the micromechanical behavior of kaolinite and the formation mechanism was revealed. Based on the radial distribution function between atoms, the cutoff distance of individual bonds inside the crystal was determined, and the evolution rules of individual bonds inside the crystal during the deformation and destruction were elucidated. Results showed that the introduction of point defects caused different degrees of reduction in the peak strength and elastic modulus of kaolinite, and the decrease was related to the loading direction, and the decline was more significant for parallel clay layers (x- and y-) than for perpendicular clay layers (z-), with pronounced anisotropy. When the defected kaolinite was extended along the x- and y-directions, the silicon‑oxygen tetrahedral and aluminum‑oxygen octahedral sheets were fractured, and the broken sites were concentrated at the defected locations; when extended along the z-direction, the failure was dominated by the fracture of interlayer hydrogen bonds. When the defective kaolinite was compressed along the x- and y-directions, the failure was mainly caused by the gradual accumulation of the bending of the clay layer, which was distinctly different from the direct fracture under the tensile condition, and when compressed along the z-direction, the clay layer collapsed until it was failure. The tendency of the broken bonds within kaolinite corresponded well with the stress-strain curve, the number of broken bonds increased with the increase of strain, and the number of broken bonds of various bonds stabilized when the crystal structure was destroyed. The bond-break types and the number of bonds broken under different simulation conditions were somewhat different, affected by the layered structure of kaolinite and the loading patterns.

Theoretical study of MoSi2/TiSi2 disilicide nanocomposites with vacancies and impurities

Research on disilicide nanocomposites, as modern materials with promising technological applications, is very desirable in these days. Our ab initio analysis concentrates on the C11b (tetragonal) MoSi2/C54 (orthorhombic) TiSi2 nanocomposites containing 14 types of interfaces formed by planes with similar arrangements (i.e. (110) planes in the C11b and (100) planes in the C54 disilicide). The most stable nanocomposites are MoSi2(AC)/TiSi2(DACB) with interfaces CD and BA and MoSi2(AD)/TiSi2(CADB) with interfaces DC and BA, both with the formation energy (related to standard element reference states) equal to −0.615 eV.atom−1 and with the lowest interface energies. In the most stable and one higher-energy interface, the effect of the impurities (Al, Si) and vacancies on the stability and structure arrangement was investigated. It turned out that: (i) Al (Si) impurities occupy Si (Ti) positions in MoSi2 (TiSi2) in the 2nd and 3rd (and 4th) layer from the interface; (ii) the interfacial Si vacancy is the most stable having the formation energy of 2.568 eV.Va−1; (iii) the least destabilising divacancy is of the Si-Si type, and (iv) Si and Al impurities simplify the formation of vacancies. As there is very little experimental information on the structure and properties of these interfaces, most of the present results are theoretical predictions which may motivate future experimental work.

The Oxidation States of Iron in Dry and Wet Olivine: A Thermodynamic Model

AbstractThe oxidation state of iron in olivine is an important control on many of its properties but is poorly constrained in mantle conditions. In this work Density Functional Theory is used to build a thermodynamic model of Fe oxidation states and incorporation mechanisms as a function of silica activity (αSiO2), pressure (P), temperature (T), oxygen fugacity (fO2), and the concentrations of Fe, H2O, Ti, and Al. Total Fe3+/∑Fe, Fe oxidation pathways and by‐products of Fe oxidation (such as Mg and Si vacancies) have a complex dependence upon αSiO2, P, T, and fO2, which are difficult to capture using simple Arrhenius relations and experiments over limited ranges. Our model predicts that in the conditions of the upper mantle, depth is the strongest control on Fe3+/∑Fe and that this relationship is strongly nonmonotonic and varies over several orders of magnitude. Fe3+/∑Fe is predicted to always be low reaching a maximum of 0.003 at around 100 km depth under normal mantle conditions though the presence of large amounts of water could increase this value further (0.03 with 500 ppmw water). While the Ferric iron concentration is predicted to be low, the concentration of Mg and Si vacancies—and thus vacancy dependent properties such as diffusion and likely strength—are predicted to be primarily a function of iron oxidation. These properties are predicted to vary by multiple orders of magnitude across the depth range of the upper mantle and thus olivine is predicted to have highly dynamic rather than static properties.

Effects of vacancy and external electric field on the electronic properties of the MoSi2N4/graphene heterostructure

Recently, the newly synthesized septuple-atomic layer two-dimensional (2D) material MoSi2N4 (MSN) has attracted attention worldwide. Our work delves into the effect of vacancies and external electric fields on the electronic properties of the MSN/graphene (Gr) heterostructure using first-principles calculation. We find that four types of defective structures, N-in, N-out, Si and Mo vacancy defects of monolayer MSN and MSN/Gr heterostructure are stable in air. Moreover, vacancy defects can effectively modulate the charge transfer at the interface of the MSN/Gr heterostructure as well as the work function of the pristine monolayer MSN and MSN/Gr heterostructure. Finally, the application of an external electric field enables the dynamic switching between n-type and p-type Schottky contacts. Our work may offer the possibility of exceeding the capabilities of conventional Schottky diodes based on MSN/Gr heterostructures.