Formation Of Silicon Nitride Research Articles

Enhancing silicon-nitride formation through ammonolysis of silanes with pseudo-halide substituents.

Considering the challenges in reactivity, potential contamination, and substrate selectivity, the ammonolysis of traditional halosilanes in silicon nitride (SiN) thin film processing motivates the exploration of alternative precursors. In this pioneering study, we employed density functional theory calculations at the M06-2X/6-311++G(3df,2p) level to comprehensively screen potential pseudo-halide substituents on silane compounds as substitutes for conventional halosilanes. Initially, we investigated the ammonolysis mechanism of halosilanes, exploring factors influencing activation barriers, with the aid of frontier molecular orbital and charge density analyses. Subsequently, a systematic screening of silane substituents from group 14 to group 16 was conducted to identify pseudo-halides with low reaction barriers. Additionally, we examined the inductive effects on pseudohalide substituents. Using cluster models to represent the silicon surface validates the realistic prediction of ammonolysis barriers with a simplified model. Our findings indicate that pseudo-halide substituents from group 16, particularly those with electron-withdrawing groups, present as practical alternatives to traditional halosilanes in SiN thin film processing, including applications such as low-temperature atomic layer deposition (ALD) techniques.

Mechanistic Investigation of the Formation of Nickel Nanocrystallites Embedded in Amorphous Silicon Nitride Nanocomposites.

Herein, we report the mechanistic investigation of the formation of nickel (Ni) nanocrystallites during the formation of amorphous silicon nitride at a temperature as low as 400 °C, using perhydropolysilazane (PHPS) as a preformed precursor and further coordinated by nickel chloride (NiCl2); thus, forming the non-noble transition metal (TM) as a potential catalyst and the support in an one-step process. It was demonstrated that NiCl2 catalyzed dehydrocoupling reactions between Si-H and N-H bonds in PHPS to afford ternary silylamino groups, which resulted in the formation of a nanocomposite precursor via complex formation: Ni(II) cation of NiCl2 coordinated the ternary silylamino ligands formed in situ. By monitoring intrinsic chemical reactions during the precursor pyrolysis under inert gas atmosphere, it was revealed that the Ni-N bond formed by a nucleophilic attack of the N atom on the Ni(II) cation center, followed by Ni nucleation below 300 °C, which was promoted by the decomposition of Ni nitride species. The latter was facilitated under the hydrogen-containing atmosphere generated by the NiCl2-catalyzed dehydrocoupling reaction. The increase of the temperature to 400 °C led to the formation of a covalently-bonded amorphous Si3N4 matrix surrounding Ni nanocrystallites.

Influence of Gas-Flow Conditions on the Evolution of Thermally Insulating Si3N4 Nano-Felts.

This paper discusses the role of nitrogen (N2) gas flow conditions on the formation of silicon nitride (Si3N4) nano-felts from polysiloxane-impregnated polyurethane (PU) foams. The polymeric foam was converted into an amorphous silicon oxycarbide (SiOC) artefact during pyrolysis, which was then transformed, at a higher temperature, into a Si3N4 felt through a reaction between the decomposition products of SiOC with N2. The study identified that a N2 flux of ~2.60 cm.min−1 at the cross-section of the furnace (controlled to 100 cm3.min−1 at the inlet of the furnace using a flowmeter) substantially favored the transformation of the parent SiOC foam to Si3N4 felts. This process intensification step significantly reduced the wastage and the energy requirement while considering the material production on a bulk scale. The study also inferred that the cell sizes of the initial PU templates influenced the foam to felt transformation.

Chip formation and wear mechanisms of SiAlON and whisker-reinforced ceramics when turning Inconel 718

Inconel 718 has found use in many demanding applications due to its high temperature fatigue strength, hardness and low thermal conductivity. These material properties present a challenge to productive and high quality (surface finish) machining and promote rapid tool wear. The work presented here describes the chip formation and wear mechanisms of silicon nitride (Si3N4) based ceramic SiAlON and silicon carbide whiskers reinforced alumina (WRA) (Al2O3 + SiCw) round (RNGN) inserts, when turning solution-annealed Inconel 718 (27<HRC<30) with a 10% concentration cutting fluid. Four sets of cutting trials were conducted at a cutting speed of 250 m/min and another four at 300 m/min. The results show that using SiAlON turning inserts at a cutting speed of 300 m/min delivered the best results in terms of tool flank wear, total tool life, and work-piece surface finish. The morphology of the Inconel 718 chip, at cutting speeds above 250 m/min, presents an intense shear band localisation in the primary shear zone of the chip/tool interface, which leads to chip segmentation.

Nitrided Silicon-Carbon Coatings Structure and Properties

The paper considers structural and physicomechanical properties of silicon-carbon coatings deposited from a gaseous medium in doping with nitrogen ions. The analysis of the coatings by X-ray photoelectron spectroscopy shows that nitriding of silicon-carbon coatings promotes the formation of silicon nitride and compounds such as CNx and SixOyNz. A 1.5–2-fold increase in the content of sp2 -hybridized carbon and silicon carbide atoms is found to prevent silicon oxidation. Thermal annealing of the resulting silicon-carbon coatings increases the content of the graphite phase and silicon oxide.It is shown that doping of the working gaswith nitrogen (Ar57% + N43%) leads to the formation of a more finely dispersed structure as compared to that when using argon only. During thermal annealing in air, the decreased carbon concentration and increased oxygen concentration can be observed due to silicon and carbon oxidation followed by desorption of carbon and oxygen compounds. In addition, annealing leads to nitrogen desorption from the coating. Nitriding of silicon-carbon coatings increases the dispersion of their structure, and heat-resistant compounds CNх, Si3N4 improve heat resistance and thermal stability of coatings, and increase microhardness and friction coefficient in friction units.

Development of dual-phase SiC/Si3N4 nanostructures on nanosized SiC particles

ABSTRACTThe present study explores the reactivity of nanosized silicon carbide (SiC) with nitrogen gas in forming silicon nitride (Si3N4). As-received micron-sized SiC particles were reduced to nanosized SiC particles by high-energy ball milling. Further, the ball-milled powders were heat-treated at 1300°C, 1400°C and 1500°C for 2 h in argon and nitrogen atmospheres. The heat-treated powders were characterised by employing X-ray diffraction, scanning electron microscopy, transmission electron microscopy, differential thermal analysis and thermogravimetric analysis. Heat-treatment in nitrogen atmosphere resulted in the development of amorphous and crystalline Si3N4 nanowires/fibers/threads from the surface of nanosized SiC particles. The morphology of developed nanostructures showed a dependence on the heat-treatment temperature. The nanosized SiC powders with nanowires/fibers/threads of Si3N4 grown on their surfaces could be used as an effective reinforcement to produce novel composites.

Tuning wettability of Si surface by ion beam induced silicon nitride formation and nanopatterning

The transformation of a hydrophilic surface to a hydrophobic surface due to chemical modification and periodic nano pattern formation on silicon surface by 5–12 keV N+ ion bombardment is reported. The reactive N+ ion bombardment at oblique angle incidence leads to form silicon nitride (Si3N4) on the surface. Also, a periodic wave-like ripple pattern is formed on Si surface at nanoscale range whose wavelength and surface roughness can be regulated by varying the ion energy (5–12 keV). It is found that the contact angle of water droplet on such patterned surface increases with the increase of ripple wavelength and surface roughness. In contrast, the contact angle does not change for the same energy Ar+ bombarded Si surfaces, where such type of surface nano patterns are absent and also surface roughness remains almost the same. The morphologies of the irradiated and un-irradiated Si surfaces are examined by Atomic Force Microscopy (AFM), whereas the surface chemical composition is investigated by X-ray photoelectron spectroscopy (XPS). The chemical modification in terms of Si3N4 formation on the surface, periodic wave-like ripple pattern formation and high increase of root mean square (rms) roughness for N+ bombarded Si surfaces result in hydrophilic to hydrophobic transformation. The tuning of wettability in terms of ion beam parameters for the patterned and chemically modified Si surfaces is discussed in detail.

Modelling Temperature Dependency of Silicon Nitride Formation Kinetic during Reaction Bonded Method

Modelling Temperature Dependency of Silicon Nitride Formation Kinetic during Reaction Bonded Method

Tailoring and investigation of surface chemical nature of virgin and ion beam modified muscovite mica

We report that the surface chemical properties of muscovite mica [KAl2(Si3Al)O10(OH)2] like important multi‐elemental layered substrate can be precisely tailored by ion bombardment. The detailed X‐ray photoelectron spectroscopic studies of a freshly cleaved as well as 12‐keV Ar+ and N+ ion bombarded muscovite mica surfaces show immense changes of the surface composition due to preferential sputtering of different elements and the chemical reaction of implanted ions with the surface. We observe that the K atoms on the upper layer of mica surface are sputtered most during the N+ or Ar+ ions sputtering, and the negative aluminosilicate layer is exposed. Inactive Ar atoms are trapped, whereas chemically reactive N atoms form silicon nitride (Si3N4) and aluminum nitride (AlN) during implantation. On exposure to air after ion bombardment, the mica surface becomes more active to adsorb C than the virgin surface. The adsorbed C reacts with Si in the aluminosilicate layer and forms silicon carbide (SiC) for both Ar and N bombarded mica surfaces. Besides the surface chemical change, prolonged ion bombardment develops a periodic ripple like regular pattern on the surface.

Construction ceramics from silicon nitride with calcium aluminates additives received by the sintering method in the SHS-reactor

The paper considers preparation of a strong and dense ceramics based on silicon nitride by sintering in a SHS reactor. As a sintering agent, an additive was used in the Al2O3-CaO system. The content of the additive varied from 5 to 15 wt. %. It is established that an increase in the amount of silicon introduced into the initial charge increases the strength characteristics of the material due to the formation of secondary silicon nitride during sintering.

Nanomechanical properties of ion induced Si ripple patterns

We report the nano-mechanical properties of ion beam induced physicochemically periodic nanostructured silicon surfaces. The periodic nano-ripple structures are developed by 8keV nitrogen ion (N+) bombardment at an oblique angle. During structure formation the nitrogen atoms are preferentially implanted at one side of the ripples, resulting in a chemical periodicity following the morphological period. X-ray photoelectron spectroscopy measurements of N+ bombarded Si surface show that the implanted nitrogen atoms form silicon nitride at the implanted zones. Atomic force microscopy height measurement shows the periodic ripple structure while the force distance curve at every point reveals spatially resolved periodic elastic modulus and adhesion properties due to site-selective nitrogen implantation and subsequent nitride formation.

Kinetics of Silicon Nitride Formation on SiO2‐Derived Rice Husk Ash Using the Chemical Vapor Infiltration Method

ABSTRACTSince silicon nitride coatings on silicon dioxide are attractive for the semiconductor and electronics industries, cognizance of their formation kinetics is crucial for optimization of production parameters. In this contribution, the deposition kinetics (rate constant and activation energy) of Si3N4 by the hybrid system chemical vapor infiltration route (HYSY‐CVI), starting from N2:NH3 and SiF4 (produced by the decomposition of Na2SiF6) has been studied. The deposition rate equation for Si3N4 was established from several possible gas‐phase or surface reaction steps involved in the growth of Si3N4 coatings onto silica‐derived rice husk ash (RHA). Based on a judicious analysis of four different models, it was found that Freundlich's adsorption model satisfactorily represents the rate of Si3N4 deposition process onto RHA.

Composition and luminescence of Si and SiO&lt;SUB align="right"&gt;2 layers co-implanted with Ga and N ions

With the aim to establish the possibility of synthesis of GaN inclusions by co-implantation of Ga and N ions in silicon and SiO2 films on a silicon substrate, the chemical composition and photoluminescence of implanted layers have been investigated. It is observed that the heavy loss of implanted atoms occurs owing to the out-diffusion (Ga from Si, and Ga and N from SiO2) in the process of post-implantation annealing. Preliminary implantation of nitrogen to form silicon nitride or oxynitride layers is shown to reduce the degree of impurity losses. In the photoluminescence spectrum of both Si and SiO2 subjected to Ga and N co-implantation, the band at 530-550 nm is present, which can be related to 'defect' luminescence of GaN.

Investigation of possibility to fabricate Si3N4-TiN ceramic nanocomposite powder by azide SHS method

The process of self-propagating high-temperature synthesis with use of a powder of sodium azide NaN3 as a nitriding agent (the SHS-Az method) was applied to fabricate a nanocomposite powder Si3N4-TiN. Combustion of the initial mixtures of NaN3 only with precursors that are halides of silicon and titanium: Na2SiF6, (NH4)2SiF6, Na2TiF6, (NH4)2TiF6 did not allow us to synthesize the composite powder of Si3N4-TiN, as the phases of silicon nitride Si3N4 were not formed. After water washing, the ultrafine powdered product of combustion consisted of one target phase of titanium nitride only and a large amount of impurity of side phases. Replacement of the halide salt of one of the elements (Si or Ti) by the powder of this element in the initial mixture of SHS-Az system resulted in formation of silicon nitride together with the titanium nitride and impurities. The least amount of impurities was obtained by burning the initial mixtures of xSi + y(NH4)2TiF6 + zNaN3 system. Only the initial mixture of 9Si + (NH4)2TiF6 + 6NaN3 allowed us to obtain as a result of the SHS-Az process the nanostructured composite powder of Si3N4-TiN without impurities.

RHEED intensities from two-dimensional heteroepitaxial nanoscale systems of GaN on a Si surface

This paper presents a computer program, which facilitates the calculation of changes to the intensity of RHEED oscillations from the heteroepitaxial structures of (0001)GaN films nucleated on a Si surface. The calculations are based on the use of a dynamical diffraction theory and different models of scattering crystal potential. New version program summaryTitle of program: RHEED_DIFF_WProgram Files doi:10.17632/hn3pt6ytky.1Licensing provisions: GNU General Public License 3Programming language used: C++Journal reference of previous version: Computer Physics Communications 185 (2014) 3001–3009Does the new version supersede the previous version?: No. It does supersede version AETW_v1_0.Reasons for the new version: Responding to the users’ feedback we presented a practical procedure of construction of simulation program, which facilitates the calculation of changes to the intensity of RHEED oscillations in the function of the glancing angle of incidence of the electron beam, employing various models of scattering crystal potential for heteroepitaxial structures of hexagonal (0001)GaN films nucleated on a Si surface. GaN has a wurtzite crystal structure with alternating planes of Ga and N atoms and lattice constants a=3.189Å and c=5.185Å [1]. Choosing the top surface to be z=0, the N atoms are located at z=nd where d=5.185/2Å and n is an integer, and Ga atoms are at z=nd−u, where u=3c/8 (as shown in Fig. 1).The nature of physical problem: Since the discovery of molecular beam epitaxy, which allows formation of layers (crystals) with a controlled composition of subsequent monolayers, the research attempts of many laboratories have been focused on studying the dynamics of formation of both monolayers and specific heterojunction structures, that is the structures with monocrystalline interfaces created by materials of various chemical compositions (different physical and chemical properties). The fundamental scientific problem in such research is to specify both interface type and growth mechanism for subsequent layers. Researchers and technologists manufacturing two-dimensional nanoscale systems frequently use RHEED rocking curves (the specular beam intensities versus the glancing angle) to control growth of films at the atomistic level of accuracy. The structural properties of the GaN/Si interface have been meticulously studied by many [3–5], and crucial problem of the direct growth of GaN on Si is the formation of amorphous silicon nitride (SiN) at the GaN/Si interface.Typical running time: The typical running time is machine and user-parameters dependent, i.e. the number of layers for both the substrate and the growing layers included in the calculations.The method of solution: RHEED intensities are calculated within the general framework described in Ref. [2] with the model of the scattering potential for heterostructures: (1)UCombined(z)=∑nUsubstrate(z)+∑n(Ulayer(z)+Uaddlayer(z)), where the Uaddlayer represents the diffuse scattering on the topmost layer.Summary of revisions: The presented version of computer program implements original algorithms of self-consistent calculations for scattering potentials GaN(0001)/Si(111) and solving a time-independent Schrödinger equation for high-energy electrons (Fig. 2). [Display omitted] [Display omitted] [Display omitted] [Display omitted] During the numerical calculations of the changes in the intensity of the specular beam in the function of the glancing angle, it was assumed that the electron energy equals 10 keV, the glancing angle was increased from 0.5° to 7°, and the value of α parameter =0.1 and β=0.5 for the MODEL3 of the scattering potential [2]. Figs. 3–4 present the situation where on the crystalline Si(111) substrate a single GaN layer was placed, where the GaN growth on Si is having a thin amorphous layer. It can be observed that for a very thin layer of GaN, a clear minimal amplitude of RHEED oscillation occurs with the coverage of the GaN layer equal to about 0.5.

Nanostructured silicon nitride from wheat and rice husks

Nanoparticles, submicron-diameter tubes, and rods of Si3N4 were synthesized from the thermal treatment of wheat and rice husks at temperatures at and above 1300 °C in a nitrogen atmosphere. The whole pattern Rietveld analysis of the observed diffraction data from treatments at 1300 °C showed the formation of only hexagonal α-phase of Si3N4 with an R-factor of 1%, whereas samples treated at 1400 °C and above showed both α- and β-phases with an R-factor of 2%. Transmission electron microscopy showed the presence of tubes, rods, and nanoparticles of Si3N4. In a two-step process, where pure SiC was produced first from rice or wheat husk in an argon atmosphere and subsequently treated in a nitrogen atmosphere at 1450 °C, a nanostructured composite material having α- and β-phases of Si3N4 combined with cubic phase of SiC was formed. The thermodynamics of the formation of silicon nitride is discussed in terms of the solid state reaction between organic matter (silica content), which is inherently present in the wheat and rice husks, with the nitrogen from the furnace atmosphere. Nanostructures of silicon nitride formed by a single direct reaction or their composites with SiC formed in a two-step process of agricultural byproducts provide an uncomplicated sustainable synthesis route for silicon nitride used in mechanical, biotechnology, and electro-optic nanotechnology applications.

Formation of cubic silicon nitride from the low-pressure phase by high-temperature shock compression

The effect of high-temperature shock compression conditions on the degree of transformation of silicon nitride into a cubic γ-modification at pressures of 36 and 50 GPa in planar recovery ampoules is studied. The x-ray Rietveld method is used to determine the quantitative phase composition before and after shock compression. The temperature reached during compression and the residual temperature after unloading are calculated. It is shown that the use of high-temperature shock compression at 36 GPa provides a higher transformation level compared to the classical approach based on the addition of copper powder into the samples.

SHS of ultrafine and nanosized Si3N4 powders: The effect of inorganic and organic additives on the microstructures, morphology, and phase compositions of products

The relationship between the microstructure and phase composition of a product obtained by selfpropagating high-temperature synthesis (SHS) and different reaction mechanisms is studied using the example of silicon nitride. The formation of nanosized silicon nitride particles upon the combustion of silicon in nitrogen and other phenomena typical of substances of this class, such as self-organization and self-assembly, are observed. The chemical condensation SHS of silicon nitride is studied in the presence of inorganic salts as modifying additives. The resulting Si3N4 powders have a structure of secondary spherical particles being composed of primary ultrafine and nanosized ones. The Si3N4 powders under study were fractionated depending on the particles size and microstructure by chemical dispersion. Ultrafine particles of the light fraction form as homogeneous rods by the conventional vapor–liquid–crystal mechanism. The fine-crystalline fractions are formed by hollow crystals assembled into globules. Microstructural analysis shows that the crystal walls consist of nanosized Si3N4 particles. The effects of organic additives introduced into the charge stock on the phase formation, microstructure formation, and particle size of SHS silicon nitride are studied. The combustion products are found to be composite powders whose phase compositions depend on the additive and the synthesis conditions. According to the data from X-ray powder diffraction and chemical analysis, the final products can contain up to 100% of β-Si3N4, up to 60% of α-Si3N4, up to 80% of SiC, and up to 70% of Si2N2O. It is shown that silicon nitride-based composite powders containing silicon carbide and/or silicon oxynitride can be obtained in one step. The role of ferric chloride hexahydrate as the SHS catalyst is studied. An ultrafine structurally homogeneous powder of β-Si3N4 is obtained in the presence of FeCl3 · 6H2O.

Phase Formation During Nitriding of Vanadium Disilicide

The evolution of microstructural and phase transformations during nitriding of mechanically preactivated vanadium disilicide powder is investigated by X-ray diffraction, chemical analysis, and transmission electron microscopy. It is established that, in the initial stage of nitriding (1000–1100°C), the phase formation is accompanied by the dispersion of near-surface zones of VSi2 particles and the formation of V2N and α-modification silicon nitride. With increase in the nitriding temperature, the phase formation is accompanied by the delamination of particles and the formation of mainly VN and silicon nitride of α- and α-modifications. Nitriding of a mechanically activated vanadium disilicide powder at 1400°C enables synthesizing a fine silicon nitride–vanadium nitride composite powder in a single process. The synthesized powder is formed as loose aggregates consisting of 50 nm particles.

Effect of Oxygen Impurity on Nitrogen Radicals in Post-Discharge Flows

Introduction Silicon nitride films (SiNx) formed at low temperature are strongly required in very shrunk LSI process. The plasma silicon nitride formation technology with low damage at low temperature has been reported [1]. We have reported that the amount of active nitridation species in the process is important to form to high quality SiNx, especially on the side wall [2]. When the oxygen impurity is remained in the process gases, the oxygen is excited during the plasma processing. Then the excited oxygen is degraded the SiNx film quality [3-6]. However, it has not been reported the effect of inactive oxygen molecules in the nitridation process. In this paper, we report the effect of the impurity oxygen in post charge flows on the process of nitride formation. Experiment Fig.1 shows the schematic diagram of the experimental setup used for the reaction products measurement in the gases. It has a mixing point placed at downstream of a Nitrogen Radical Generator [7]. The produced gases reacted from the nitrogen radicals and O2 gas are measured by Fourier Transform Infrared spectroscopy (FTIR). The impurity concentration of oxygen in N2 gas was less than 1 ppb, this indicates the oxygen impurity of supply gas did not affect the experimental results. Nitrogen radicals concentration was generated by the Nitrogen Radical Generator several ten ppm in the N2 gas [7]. The pressure in Nitrogen Radical Generator was varied from 30 to 120 kPa in the case of the N2 flow rate at 5, 7, and 10slm. The O2flow rate were varied from 8 to 190 sccm. Results and discussions Fig. 2 show the absorbance of (a)O3, (b)N2O produced from the nitrogen radicals and O2gas. Horizontal axis of Fig. 2(a) denotes the product of the oxygen partial pressure and the oxygen molecules concentration. Here, this is equivalent to the collision probability of the oxygen molecules and the oxygen molecules. The produced O3concentration increases with the increase of the collision probability. Then, horizontal axis of Fig. 2(b) denotes the product of the oxygen partial pressure and the elements' density exception of the oxygen molecules, that is, they’re nitrogen molecules and nitrogen radicals. Here, this is equivalent to the collision probability of the oxygen molecules and the nitrogen molecules including the nitrogen radicals. The produced N2O concentration decreases with the increase of the collision probability. The oxygen molecules become oxygen radicals by the colliding with the nitrogen radicals because only O3 and N2O are generated. It’s considered that the numbers of nitrogen radicals decrease at the collision with oxygen molecules. Then, Fig. 2(a) and (b) show the oxygen radicals are more easier to react to the oxygen molecules or the oxygen radicals than the nitrogen molecules or the remained nitrogen radicals. The nitrogen radicals easily transfer the energy to the oxygen, and the nitrogen become inactive. These results indicates that the oxygen impurity has strong impact on the radical nitridation process. The oxygen components, even O2molecules, must be reduced in the process using nitrogen radicals. Acknowledgement This research has been carried out at fluctuation free facility of New Industry Creation Hatchery Center, Tohoku University.