Si Vacancies Research Articles

Co-sputtering deposition of high-photoresponsivity and high-mobility polycrystalline BaSi2 films on Si substrates

• Stoichiometric BaSi 2 films were obtained by co-sputtering from BaSi 2 and Ba targets. • Power applied on the targets controlled the Ba and Si species reaching the substrate. • Deposition without Ba target resulted in Ba-deficient films. • Large photoresponsivity was observed in spite of polycrystalline films. Barium disilicide (BaSi 2 ) has shown great promise for solar cell applications. Recent studies have revealed that defects such as Si vacancies in BaSi 2 films caused by the Ba/Si atomic ratios being away from stoichiometry degrade the electrical and photoresponse properties of BaSi 2 films. The formation of BaSi 2 films by sputtering has been performed using basically one BaSi 2 target, which makes it difficult to control the Ba/Si atomic ratio of the grown films. In this work, we investigate the formation of BaSi 2 films on Si(111) substrates by radio-frequency (RF) sputtering of BaSi 2 and Ba targets, and independently control the RF powers set on the targets. It is found that the contribution of sputtering the Ba target to the BaSi 2 growth rate ( GR Ba / GR BaSi2 ) can be used to find the growth conditions for high-photoresponsivity BaSi 2 films. The highest photoresponsivity reached 1.4 A W −1 at room temperature for BaSi 2 films grown at 600°C when a bias voltage of 0.5 V was applied between the front indium tin oxide electrodes and rear Al electrodes. The electron mobility depended on sputtering conditions, but mostly exceeded 1000 cm 2 V −1 s −1 in spite of randomly oriented polycrystalline films. These values are comparable to those obtained for BaSi 2 epitaxial films on Si(111) by molecular beam epitaxy.

The corrosion behavior of CVD SiC coatings on SiCf/SiC composites in a simulated molten salt reactors environment

The corrosion behavior of SiC coatings deposited at 1000, 1150 and 1200 ℃ on SiCf/SiC composites was investigated. CVD SiC coatings deposited at higher temperatures provided better corrosion resistance in molten salt. SiC coating at 1200 ℃ showed the best resistance due to the high crystallinity. In addition, multi-scale characterization revealed that the dissolution of Si into molten salt resulted in the formation of a C-rich amorphous layer on SiC coatings. The fluorine was observed to diffuse through corrosion layer. According to DFT calculation, the diffusion of molten salt elements was assisted with Si vacancies and fluorine diffused fastest.

Effects of vacancies on structural, electronic, mechanical, and thermodynamic properties of C40-VSi2

ABSTRACT In our work, to figure out the effects of V and Si vacancies on formation energies, elastic properties, phonon dispersions, electronic structures, and thermodynamic properties of VSi2, we used first-principles calculations. VSi2 with V and Si vacancies are dynamically and thermodynamically stable from the calculated formation energies and phonon dispersions. Moreover, VSi2 with V and Si vacancies are mechanically stable certified by single-crystal elastic constants. The presence of different atomic vacancies can weaken the bond strength of V–Si and Si–Si bonds, and eventually leads to the decreasing phase stability and elastic modulus, but can increase elastic anisotropy and ductileness. Finally, thermodynamic properties, including Debye temperature, sound velocities, and directional sound velocities, of perfect VSi2 and VSi2 with different vacancies are calculated. Highlights Based on the calculated vacancy formation energies and phonon dispersions, the perfect VSi2 and VSi2 with different vacancies are thermodynamically and dynamically stable. The vacancies can reduce the thermodynamical stability of VSi2, VSi2 with V vacancies are more stable than those with Si vacancies, and among VSi2 with vacancies, VSi2 with V-Va1 is the most stable. The perfect VSi2 and VSi2 with different vacancies are brittle, and the atomic vacancies can improve the ductility of VSi2 slightly, but can weaken the elastic modulus. The order of elastic anisotropy is Si-va3 > Si-va1 > Si-va2 > V-va2 > V-va1 > perfect VSi2. The Si–Si and V–Si bonds are broken after Si or V atoms removed, resulting in the decreasing bond strength in VSi2 with vacancies, and eventually leading to the lower phase stability and elastic moduli of VSi2 with vacancies compared to the perfect VSi2. The calculated sound velocities also show anisotropy.

A Multi-Scale Simulation Study of Irradiation Swelling of Silicon Carbide.

Silicon carbide (SiC) is a promising structural and cladding material for accident tolerant fuel cladding of nuclear reactor due to its excellent properties. However, when exposed to severe environments (e.g., during neutron irradiation), lattice defects are created in amounts significantly greater than normal concentrations. Then, a series of radiation damage behaviors (e.g., radiation swelling) appear. Accurate understanding of radiation damage of nuclear materials is the key to the design of new fuel cladding materials. Multi-scale computational simulations are often required to understand the physical mechanism of radiation damage. In this work, the effect of neutron irradiation on the volume swelling of cubic-SiC film with 0.3 mm was studied by using the combination of molecular dynamics (MD) and rate theory (RT). It was found that for C-vacancy (CV), C-interstitial (CI), Si-vacancy (SiV), Si-interstitial (SiI), and Si-antisite (SiC), the volume of supercell increases linearly with the increase of concentration of these defects, while the volume of supercell decreases linearly with the increase of defect concentration for C-antisite (CSi). Furthermore, according to the neutron spectrum of a certain reactor, one RT model was constructed to simulate the evolution of point defect under neutron irradiation. Then, the relationship between the volume swelling and the dose of neutrons can be obtained through the results of MD and RT. It was found that swelling typically increases logarithmically with radiation dose and saturates at relatively low doses, and that the critical dose for abrupt transition of volume is consistent with the available experimental data, which indicates that the rate theory model can effectively describe the radiation damage evolution process of SiC. This work not only presents a systematic study on the relationship between various point defect and excess volume, but also gives a good example of multi-scale modelling through coupling the results of binary collision, MD and RT methods, etc., regardless of the multi-scale modelling only focus on the evolution of primary point defects.

Multimodal bioimaging using nanodiamond and gold hybrid nanoparticles

Hybrid core–shell nanodiamond-gold nanoparticles were synthesized and characterized as a novel multifunctional material with tunable and tailored properties for multifunctional biomedical applications. The combination of nanostructured gold and nanodiamond properties afford new options for optical labeling, imaging, sensing, and drug delivery, as well as targeted treatment. ND@Au core–shell nanoparticles composed of nanodiamond (ND) core doped with Si vacancies (SiV) and Au shell were synthesized and characterized in terms of their biomedical applications. Several bioimaging modalities based on the combination of optical and spectroscopic properties of the hybrid nano-systems are demonstrated in cellular and developing zebrafish larvae models. The ND@Au nanoparticles exhibit isolated ND’s Raman signal of sp3 bonded carbon, one-photon fluorescence of SiV with strong zero-phonon line at 740 nm, two-photon excited fluorescence of nanogold with short fluorescence lifetime and strong absorption of X-ray irradiation render them possible imaging agent for Raman mapping, Fluorescence imaging, two-photon Fluorescence Lifetime Imaging (TP-FLIM) and high-resolution hard-X-ray microscopy in biosystems. Potential combination of the imaging facilities with other theranostic functionalities is discussed.

Controls on the distribution of hydrous defects in forsterite from a thermodynamic model

The distribution of hydrogen across different crystallographic sites and point defects in forsterite determines how many properties, such as rheology, conductivity and diffusion are affected by water. In this study, we use lattice dynamics and Density Functional Theory (DFT) to build a thermodynamic model of H-bearing defects in Al,Ti bearing forsterite. From this, the distribution of hydrogen in forsterite as a function of pressure (P), temperature (T), water, Al and Ti concentration is determined. Primarily, hydrogen distribution in forsterite is complex and highly varied in different P, T and composition regimes. Therefore, extrapolation of properties that depend upon water between these different regimes is non-trivial. This extrapolation has often been done by determining exponents which describe how defect-specific defect concentrations or properties dependent upon them vary with water concentration/fugacity. We show here that these exponents can vary radically across common experimental and geophysical P, T and [H2O]bulk ranges as the favoured hydrogen-bearing defects change. In general, at low pressures hydrogen favours Mg vacancies (high temperatures) or complexes with titanium (low temperatures) whilst at high pressures, hydrogen favours Si vacancies regardless of all other conditions. Higher values of [H2O]bulk also favours hydrated Si vacancies. We evaluate these distributions along geotherms and find that hydrogen distribution and thus its effect on forsterite properties is highly varied across the expected conditions of the upper mantle and thus cannot be simply represented. No such distribution of hydrogen has been previously constructed and it is essential to consider this hydrogen distribution when considering the properties of a wet mantle.

Influence of Point Defects on the Equilibrium Concentration of Interstitial Oxygen in Crystalline Silicon

The effect of excess point defects on the equilibrium concentration of interstitial oxygen for the system of interstitial oxygen/SiO2 precipitates in crystalline Si is theoretically investigated. The expression for the equilibrium concentration of interstitial oxygen in Si modified by the excess point defects is derived. Excess vacancies in Si are found to decrease this concentration, while the excess Si self-interstitials have the opposite effect. The effects of different conditions for the point defect generation on the equilibrium in the system of interstitial oxygen/SiO2 precipitates in crystalline Si are studied.

Molecular dynamics study of effects of point defects on thermal conductivity in cubic silicon carbide

Silicon carbide (SiC) has been widely used in nuclear technology due to its excellent properties. In the irradiation environment, the energetic incident particles can cause the atoms in the material to deviate from the position of the crystal lattice, thereby producing the vacancies, interstitial atoms, anti-site atoms and other point defects. These defects will change the thermal properties of the material and degrade the service performance of the material. Therefore, in this work the equilibrium molecular dynamics method (Green-Kubo method) is used to study the effect of point defects on the heat transfer properties of cubic SiC (<i>β</i>-SiC or 3<i>C</i>-SiC) with the help of the Tersoff-type potential. The point defects considered include Si interstitial atoms (Si<sub>I</sub>), Si vacancies (Si<sub>V</sub>), Si anti-site atoms (Si<sub>C</sub>), C interstitial atoms (C<sub>I</sub>), C vacancies (C<sub>V</sub>) and C anti-site atoms (C<sub>Si</sub>). It is found that the thermal conductivity (<i>λ</i>) decreases with the increase of the point defect concentration (<i>c</i>). The excessive thermal resistance (Δ<i>R</i> = <i>R</i><sub>defect </sub>– <i>R</i><sub>perfect</sub>, <i>R</i> = 1/<i>λ</i>, <i>R</i><sub>defect</sub> is the thermal resistance of the defective material, and <i>R</i><sub>perfect</sub> is the thermal resistivity of the material without defects) has a linear relation with the concentration of point defects in the considered range (0.2%–1.6%), and its slope is the thermal resistivity coefficient. It can be found that the thermal resistivity coefficient of vacancy and interstitial atoms are higher than that of anti-site atoms; the thermal resistivity coefficient of point defects at high temperature is higher than at low temperature; the thermal resistivity coefficient of Si vacancies and Si interstitial atoms are higher than that of C vacancies and C interstitial atoms. These results are helpful in predicting the thermal conductivity of silicon carbide under irradiation and controlling the thermal conductivity of silicon carbide.

A Study on the Isolation Ability of LOCal Oxidation of SiC (LOCOSiC) for 4H-SiC CMOS Process

The oxidation rate of SiC can be greatly enhanced by pre-amorphization ion-implantation (PAI), and the PAI process has been employed to form the LOCal Oxidation of SiC (LOCOSiC) structure for device isolation in SiC integrated circuits (ICs). This work presents the study on the defect layer below the thermally grown SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the impact of the defect layer on devices. The deep-level transient spectroscopy (DLTS) analysis reveals that the defect layer consists lots of C vacancies and Si vacancies. The leakage current of the edge-intensive N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /P-junction exhibits stronger temperature dependence than that of the P <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /N-junction. This result confirms that C vacancy is an effective lifetime killer in n-type SiC, but not in p-type SiC. Although these defects increase the leakage current of the edge-intensive SiC N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /P-junction by 42 times at 150 °C compared with the junction with conventional chemical vapor deposited (CVD) field oxide (FOX), the leakage current is still much lower than the required OFF-state current of ICs. The defect layer has high resistance, and it is hard to let the SiC surface into inversion state so that the threshold voltage of the field MOSFET is higher than ±24 V.

Density Functional Theory Study on Anisotropic Arrangement of Interstitial Oxygen Atoms at (001) Interface of Oxide Precipitates in Si Crystal

The stability of the anisotropic oxygen (O) arrangement at the (001) interface of oxide precipitate (OP) in a Si crystal was analyzed by the density functional theory to understand the OP/Si interfacial structure and the gettering mechanism at the interface at an atomic level. In contrast to the case of the Si bulk, the O atoms align in one Si–Si zig-zag bond to some extent, then start to occupy other Si–Si bonds. After the O atoms are arranged in multiple series in the first interface layer to some extent, those in the second layer become more stable. This trend was confirmed for the second and third layers. The results support the existence of an experimentally observed transition layer with a composition of SiO x (x < 2) at the interface [Kissinger et al., ECS J. Solid State Sci. Technol., 9, 064002 (2020)]. Furthermore, several O alignments at the interface drastically reduce the formation energy of Si vacancies. The vacancies at the OP/Si interface were found to be effective gettering sites for Cu while the dangling bond was found to be an effective gettering site for Ni with a binding energy exceeding 1 eV.

Microstructural Analysis of Novel Preceramic Paper-Derived SiCf/SiC Composites.

This paper presents the results of microstructural analysis of novel preceramic paper-derived SiCf/SiC composites fabricated by spark plasma sintering. The sintering temperature and pressure were 2100/2200 °C and 60/100 MPa, respectively. The content of fibers in the composites was approx. 10 wt %. The SiCf/SiC composites were analyzed by positron annihilation methods, X-ray diffraction technology, scanning electron microscopy, and Raman spectroscopy. Longer sintering time causes the proportion of the 6H-SiC composition to increase to ~80%. The increase in sintering temperature from 2100 °C to 2200 °C leads to partial transition of 4H-SiC to 6H-SiC during the sintering process, and the long-life component of positrons indicates the formation of Si vacancies. The Raman characteristic peaks of turbostratic graphite appear in the Raman spectrum of SiC fibers, this is caused by the diffusion of carbon from the surface of the SiC fiber and the preceramic paper during the high-temperature sintering process.

Inducing Half-Metallicity in Monolayer MoSi2N4.

First-principles calculations are performed for the recently synthesized monolayer MoSi2N4 [Science 369, 670–674 (2020)]. We show that N vacancies are energetically favorable over Si vacancies, except for Fermi energies close to the conduction band edge in the N-rich environment, and induce half-metallicity. N and Si vacancies generate magnetic moments of 1.0 and 2.0 μB, respectively, with potential applications in spintronics. We also demonstrate that N and Si vacancies can be used to effectively engineer the work function.

The role of Si vacancies in the segregation of O, C, and N at silicon grain boundaries: An ab initio study.

Grain boundaries (GBs) are defects originating in multi-crystalline silicon during crystal growth for device Si solar cell fabrication. The presence of GBs changes the coordination of Si, making it advantageous for charge carriers to recombine, which brings a significant reduction of carrier lifetimes. Therefore, GBs can be highly detrimental for device performances. Furthermore, GBs easily form vacancies with deep defect electronic states and are also preferential segregation sites for various impurity species, such as C, N, and O. We studied from first principles the correlation between structural, energetics, and electronic properties of the Σ3{111} Si GB with and without vacancies, and the segregation of C, N, and O atoms. C and O atoms strongly increase their ability to segregate when vacancies are present. However, the electronic properties of the Σ3{111} Si GB are not affected by the presence of O, while they can strongly change in the case of C. For N atoms, it is not possible to find a clear trend in the energetics and electronic properties both with and without vacancies in the GB. In fact, as N is not isovalent with Si, as C and O, it is more flexible in finding new chemical arrangements in the GB structure. This implies a stronger difficulty in controlling the properties of the material in the presence of N impurity atoms compared to C and O impurities.

Effects of Ba-to-Si deposition rate ratios on the electrical and photoresponse properties of arsenic-doped n-type BaSi2 films

The formation of high-quality impurity-doped n-type BaSi2 films is inevitable for their use in solar cell applications. We grew arsenic (As)-doped n-type BaSi2 epitaxial films by molecular beam epitaxy with Ba-to-Si deposition rate ratios (RBa/RSi) varied in the range 0.8−3.9, and investigated their effect on the electrical and photoresponse properties of grown films. As-doped BaSi2 films showed n-type conductivity with an electron concentration of the order of 1016 cm−3 at room temperature regardless of the RBa/RSi. The full-width at half maximum of an Ag mode Raman peak (∼490 cm−1) decreased for samples grown under Si-rich conditions. This result indicates the decrease in Si vacancies acting as recombination centers in BaSi2 since this Raman peak position is close to that caused by Si vacancies. This is consistent with the result that the photoresponsivity reached a maximum in BaSi2 films prepared under Si rich conditions (RBa/RSi = 1.3). However, further Si-rich conditions (RBa/RSi = 0.8) led to the degradation of photoresponsivity. Photoluminescence spectra showed that the position of localized states changed depending on RBa/RSi, indicating that the type of defects changed in the BaSi2 films.

The effects of vacancies defects and oxygen atoms occupation on physical properties of chromium silicide from a first-principles calculations

In present work, the effects of vacancy defects on the mechanical and thermodynamic properties of Cr5Si3 have been investigated using the first-principles. The occupation mechanism of oxygen atoms in Cr5Si3 is also carefully analyzed and discussed. The vacancy formation, lattice vibrations, electronic structure, elasticity and thermodynamic parameters of Cr5Si3 were calculated separately. The results show that Cr5Si3 is stable and irrespective of the presence of vacancies or oxygen atoms occupation in it. In addition, the Si vacancies cause Cr5Si3 to undergo a brittle to ductile transition, which originates the weak hybridization between Cr and Si atoms. Importantly, when the Si-Va2 vacancy is occupied by oxygen atom, Cr5Si3 undergoes a brittle to ductile transition despite its poor hardness and resistance to deformation, which is attributed to the formation of weak Cr–O bonds. Furthermore, both the presence of vacancy defects and the introduction of oxygen atoms result in Cr5Si3 exhibiting the greater phase stability and better thermal properties.

Self-diffusion mechanisms based defect complexes in MoSi2

MoSi2 is widely concerned due to excellent electrical conductivity, oxidation resistance as a typical transition metal silicide. The high-temperature diffusion behavior is one of the important factors for the degradation of MoSi2 coatings. However, the diffusion mechanism in MoSi2 is still unclear. Prior theoretical work mostly focused on defect formation energy, but these are not consistent with the self-diffusion experiments because the migration behaviors were not considered. Therefore, the purpose of this work was to investigate the microscopic diffusion mechanisms of Mo and Si atoms in MoSi2 using density functional theory and the CI-NEB method. We confirmed that the temperature-dependent vibrational contribution has a significant impact on the defect formation free energy. The isolated point defects in MoSi2 will tend to aggregate to form defect complexes, which participate in the atomic diffusion as mediators. The defect migration behaviors of atoms for vacancy mediated, vacancy complex mediated, and antisite assisted jumps were obtained based on electronic structures analysis. The results show that Si diffusion is mediated by intrasublattice jumps of the nearest neighbor Si vacancies. Moreover, the destroyed covalent Mo–Si bonds by Si vacancies and the non-directional weak metal bonds formed by the Mo antisites and Mo atoms could improve the mobility of the Mo atom which results in the low migration barrier. The agreement between our calculations and the reported experimental results indicates that the dominant diffusion mechanism for Mo atoms is mediated by vacancy complex mediated jumps and antisite assisted jumps. It is concluded that the Si vacancy-based defect complexes are likely the diffusion mediators for Mo atom self-diffusion in MoSi2. This work provides a deeper insight into the connection between the atomic mechanism and the macroscopic behavior for the diffusion in the MoSi2, and establishes the basis for further optimizing high-temperature coating materials.

Resolving Jahn-Teller induced vibronic fine structure of silicon vacancy quantum emission in silicon carbide

Point defects in semiconductors are promising single-photon emitters (SPEs) for quantum computing, communication, and sensing applications. However, factors such as emission brightness, purity. and indistinguishability are limited by interactions between localized defect states and the surrounding environment. Therefore, it is important to map the full emission spectrum from each SPE, to understand the complex interplay between the different defect configurations, their surroundings, and external perturbations. Herein, we investigate a family of regularly spaced sharp luminescence peaks appearing in the near-infrared portion of photoluminescence (PL) spectra from $n$-type 4H-SiC samples after irradiation. This periodic emitter family, labeled the L lines, is only observed when the zero-phonon line signatures of the negatively charged Si vacancy (so-called V lines) are present. The L lines appear with $1.45\phantom{\rule{0.28em}{0ex}}\mathrm{meV}$ and $1.59\phantom{\rule{0.28em}{0ex}}\mathrm{meV}$ energy spacing after H and He irradiation and increase linearly in intensity with fluence---reminiscent of the intrinsic defect trend. Furthermore, we monitor the dependence of the L-line emission energy and intensity on heat treatments, electric field strength, and PL collection temperature, discussing these data in the context of the L lines. Based on the strong similarity between the irradiation, electric field, and thermal responses of the L and V lines, the L lines are attributed to the Si vacancy in 4H-SiC. The regular and periodic appearance of the L lines provides strong arguments for a vibronic origin explaining the oscillatory multipeak spectrum. To account for the small energy separation of the L lines, we propose a model based on rotations of distortion surrounding the Si vacancy driven by a dynamic Jahn-Teller effect.

First-principles study of the effect of vacancies on the interface stability of 3C-SiC/Mg composites based on theoretical physical method

In this paper, the first principles calculation method based on theoretical physics method was used to optimize the structure of 3C-SiC(111)/Mg(0001) interface model with vacancies. The interface adhesion work, vacancy formation energy and electronic structure were calculated and analyzed. The results show that the interface adhesion work of 3C-SiC/Mg-VMg −1、3C-SiC/Mg-VMg −2、3C-SiC/Mg-VMg −3 is greater than that of 3C-SiC/Mg which indicates that Mg vacancy have a certain promoting effect on the interface bonding of 3C-SiC/Mg, and the interface adhesion work of 3C-SiC/Mg- VMg − 1 is the largest. Because after the presence of Mg vacancy, the number of wavelet peaks increases and the pseudo-energy gap increases, so that the covalent bond increases and the interface adhesion work increases. Their vacancy defect formation energies are not much different, which are 1.1057eV, 1.0584eV, 1.2299eV, respectively. After the presence of C vacancy and Si vacancy, the interface adhesion work of 3C-SiC-VC − 1/Mg 、3C-SiC-VC − 3/Mg、3C-SiC-VSi − 2/Mg and 3C-SiC-VSi −4/Mg is smaller than that of 3C-SiC/Mg, which indicates that C vacancy and Si vacancy have no effect on the interface bonding. Among them, the interface adhesion work of 3C-SiC-VC −1/Mg is greater than that of 3C-SiC-VC −3/Mg, and the interface adhesion work of 3C-SiC-VSi −4/Mg is greater than that of 3C-SiC-VSi −2/Mg. After the presence of vacancy, the number of small wave peaks in the density of states map becomes less, the distribution of the density of states near the Fermi level becomes narrower, the metallicity is enhanced, and the bond strength decreases. In terms of the formation energy of vacancy defects, the formation energy of 3C-SiC-VC − 1/Mg is less than that of 3C-SiC-VC − 3/Mg, and the formation energy of 3C-SiC-VSi − 2/Mg is less than that of 3C-SiC-VSi − 4/Mg.

Hyperdynamics simulations with ab initio forces.

By applying the locally optimal rotation method to deal with the lowest eigenvalue of a Hessian matrix, we have efficiently incorporated the hyperdynamics method into the ab initio scheme. In the present method, we only need to calculate the first derivative of the potential and several more force calls in each molecular dynamics (MD) step, which makes hyperdynamics simulation applicable in ab initio MD simulations. With this implementation, we are able to simulate defect diffusion in silicon with boost factors up to 105. We utilized both direct MD and the hyperdynamics method to investigate diffusion of lithium atoms and silicon vacancies in silicon. We identified the complex diffusion process. The obtained diffusion coefficients of Li atoms and Si vacancies are in good agreement with the direct MD results.

Electronic property of intrinsic point defect system on β–Si3N4(0001) surface

The intrinsic point defect influence data for [Formula: see text]–Si3N4by far are incomplete and experimental clarification is not easy. In this contribution, the effects of vacancy ([Formula: see text], [Formula: see text] and [Formula: see text]) and interstitial ([Formula: see text] and [Formula: see text]) defects on the electronic properties of H-passivated [Formula: see text]–Si3N4(0001) surface are explored based on density functional theory (DFT) calculation. The results show that it is easier to form [Formula: see text] vacancy defects in the surface layer under Si-rich conditions. The existence of N vacancies makes the bottom of conduction bands shift downwards, and the top of valance band is away from Fermi level. The presence of [Formula: see text] makes the system have the characteristics of p-type semiconductor, and the closer to the inner layer, the narrower the range of additional energy bands and the greater the degree of localization of electrons. The closer the Si atom vacancy is to the surface, the smaller the photon energy corresponding to the maximum absorption coefficient is. Compared with the N vacancy system, the Si vacancy system has higher reflection ability in the low energy region. For the interstitial defect systems, [Formula: see text] is easy to form on the surface layer, and [Formula: see text] is easy to produce in the inner layer. The [Formula: see text] system has a new additional energy level at the Fermi level, and as the [Formula: see text] is closer to the inner layer, the energy range of the additional energy level is also narrower. In the [Formula: see text] system, the new additional energy levels appear at the Fermi level and the intermediate band. The results have positive significance for the design of this advanced structural and functional integrated ceramics. The absorption coefficient and reflection coefficient of [Formula: see text] system are much higher than those of other systems when the energy is greater than 2.5 eV.