Silicon Atoms Research Articles

Near-surface damage and mixing in Si-Cl2-Ar atomic layer etching processes: Insights from molecular dynamics simulations

Silicon-chlorine-argon (Si-Cl2-Ar) atomic layer etching (ALE) is simulated using classical molecular dynamics (MD). The simulations provide a detailed view into the near-surface region during ALE processing. Bombardment of Ar+ ions creates a mixed amorphous region that significantly differs from the picture of ideal ALE. There is also a significant change in the Si etch yield and the etch product distribution as a function of Ar+ ion fluence. The Si etch yield is the highest at the beginning of the bombardment step but eventually decays to the physical sputtering yield. Atomic Cl and silicon chlorides are major etch products at the start of an ion bombardment step, but quickly decay. Atomic Si yields remain relatively constant as a function of Ar+ ion fluence. A new schematic of Si-Cl2-Ar ALE is presented in order to emphasize the complex behavior observed in MD simulations.

New 3-Aminopropylsilatrane Derivatives: Synthesis, Structure, Properties, and Biological Activity.

The biologically active compound 3-aminopropylsilatrane (a compound with a pentacoordinated silicon atom) underwent an aza-Michael reaction with various acrylates and other Michael acceptors. Depending on the molar ratio, the reaction yielded Michael mono- or diadducts (11 examples) containing functional groups (silatranyl, carbonyl, nitrile, amino, etc.). These compounds were characterized via IR and NMR spectroscopy, mass spectrometry, X-ray diffraction, and elemental analysis. Calculations (using in silico, PASS, and SwissADMET online software) revealed that the functionalized (hybrid) silatranes were bioavailable, druglike compounds that exhibited pronounced antineoplastic and macrophage-colony-stimulating activity. The in vitro effect of silatranes on the growth of pathogenic bacteria (Listeria, Staphylococcus, and Yersinia) was studied. It was found that the synthesized compounds exerted inhibitory and stimulating effects in high and low concentrations, respectively.

Effect of Prior Boriding on Microstructure and Mechanical Properties of Nanobainitic X37CrMoV5-1 Hot-Work Tool Steel.

The influence of prior pack boriding on the microstructure and properties of nanobainitised X37CrMoV5-1 hot-work tool steel was investigated in the present work. Pack boriding was conducted at 950 °C for 4 h. Nanobainitising consisted of two-step isothermal quenching at 320 °C for 1 h, followed by annealing at 260 °C for 18 h. A combination of boriding with nanobainitising constituted a new hybrid treatment. The obtained material exhibited a hard borided layer (up to 1822 ± 226 HV0.05) and a strong (rupture strength 1233 ± 41 MPa) nanobainitic core. However, the presence of a borided layer decreased mechanical properties under tensile and impact load conditions (total elongation decreased by 95% and impact toughness by 92%). Compared with borided and conventionally quenched and tempered steel, the hybrid-treated material retained higher plasticity (total elongation higher by 80%) and higher impact toughness (higher by 21%). It was found that the boriding led to the redistribution of carbon and silicon atoms between the borided layer and substrate, which could influence bainitic transformation in the transition zone. Furthermore, the thermal cycle in the boriding process also influenced the phase transformations during subsequent nanobainitising.

Increasing the Efficiency of Silicon Solar Elements by Doping with Nickel

It is shown that in the near-surface region of the solar cells (SCs) the concentration of nickel atoms is higher than in the bulk by 2–3 orders of magnitude, therefore, the gettering rate in the near-surface region is higher. Optimal modes of gettering by nickel clusters (i.e., nickel diffusion – Т = 800–850 °С, additional thermal annealing – Т = 750–800 °С) and the structure of a silicon SC were experimentally determined, which makes it possible to increase the efficiency of silicon SCs by 25–30% relative to the control. The physical mechanisms of the influence of the processes of diffusion of impurity nickel atoms and additional thermal annealing on the state of nickel atoms in the near-surface region and the SCs base and, accordingly, on the parameters of the SC are revealed. Physical models of the structure of a cluster of nickel atoms in silicon and the process of fast diffusing impurities gettering by clusters of nickel atoms are created. The binding energy of fast dissusing impurities atoms with a nickel cluster is estimated to be ~ 1.39 eV. The calculation shows that doping with nickel can increase the lifetime of minority charge carriers by 2–4 times, and the collection coefficient by 1.4–2 times. The experiment showed an increase in the minority charge carriers lifetime up to 2 times and an increase in efficiency by 25–30%.

Coordination-Induced Migration of Aryl Groups in the Reactions of a Dialkylsilanone with a Series of Triarylboranes.

Although carbonyl compounds are activated by the coordination of a Lewis acid to the carbonyl oxygen atom, a similar activation process of R2 Si=O species remains unclear. We report herein the reactions of a silanone (1, Scheme 1) with a series of triarylboranes to afford the corresponding boroxysilanes. Experimental results and computational studies indicate that the electrophilicity of the unsaturated silicon atom is enhanced by the complexation of 1 with triarylboranes, and the subsequent aryl migration from the boron atom to the electrophilic silicon atom proceeds.

Stability of Graphene on the Si (111) Surface: Insights from Reactive Molecular Dynamics Simulations

The remarkable characteristics of graphene render it well-suited for a diverse range of applications, particularly in the realm of electronic devices. After the synthesis process, the two-dimensional material known as graphene is then transferred onto a substrate. Silicon (Si) is considered a suitable choice for this purpose. Therefore, it has become essential to investigate the stability of graphene on silicon surfaces. This study utilized reactive molecular dynamics simulations to investigate the thermal stability of graphene on a Si (111) substrate across a temperature range of 300 to 1500 K. The results demonstrate the exceptional stability of graphene on this particular surface. This phenomenon can be explained by the restricted intermolecular interactions between the carbon atoms in graphene and the silicon atoms on the substrate surface. The study findings indicate that graphene exhibits a dome-shaped configuration on the Si (111) surface. In this configuration, only the carbon atoms located at the periphery of the graphene structure interact with the silicon atoms present on the underlying substrate.

Internal hydrophobization of cement-based materials by means of silanes

The paper shows the opportunity of application of an organosilicon compound such as triethoxyoctylsilane (OTES) containing long, hydrophobic alkyl sidechains (octyl groups – C8H17) attached to the silicon atoms, as the admixtures for internal hydrophobization of cementitious building materials characterized by a porous internal structure. The study included the cement paste, mortar and concrete with three different hydrophobic admixtures based on triethoxyoctylsilane, but with miscellaneous concentration of the triethoxyoctylsilane in the admixture and different dosage in the fresh mix. The impact of organosilicon hydrophobic admixtures on the mechanical properties such as compressive strength, capillary water absorption of the cement mortar and concrete and the microstructure of cement paste was investigated. The hydrophobic, silicon-based admixtures decrease the capillary water absorption coefficient significantly. Even by 81.1% in case of cement mortar. The mechanical strength of cement mortar is also decreased, by 23.6%. The noticeable changes in the internal structure of pores of cement paste only for one admixture is observed.

Improvement of Interface Properties for Thermally Oxidized SiC/SiO<sub>2</sub> MOS Capacitor by Post Oxidation Annealing Treatment

In this work, we report an innovative approach to improve the interface properties of SiC/SiO2 metal oxide semiconductor (MOS) capacitors. High temperature (1350°C) oxidation under different ambient is followed by a combination of post-oxidation annealing (POA) treatments using N2, N2O and NO gases. TOF-SIMS analysis shows silicon and nitrogen peaks near the SiC/SiO2 interface. The silicon peak is attributed to the emission of silicon and carbon atoms during high temperature oxidation. The accumulation of nitrogen is caused by the presence of nitrogen during oxidation or POA. One of the lowest interface-trap densities along with good dielectric strength has been demonstrated with the N2 and NO gas POA treatment.

Xenon ion implantation induced defects and amorphization in 4H–SiC: Insights from MD simulation and Raman spectroscopy characterization

Xenon Focused Ion Beam (Xe-FIB) processing of 4H–SiC is an emerging technique with great potential for various applications. In this study, we investigate the evolution mechanism of damage caused by xenon ion implantation in 4H–SiC using a combination of molecular dynamics (MD) simulation and Raman spectroscopy. The study explores the microscopic mechanisms of damage processing and repairs using the proper potential function and the optimized simulation model. The MD simulation reveals that the vacancy and interstitial sites of silicon and carbon atoms, as identified by the Wigner-Seitz defect method, increase linearly with implanted dose until the dose reaches 2 × 1014 ions/cm2. Subsequently, the growth rate of each defect site in the damaged area slows down and eventually comes to a saturation state with a continuous increase in dose. The growth rate of the amorphous region also slows down with the constant increase in dose, similar to the results obtained through variable temperature Raman spectroscopy characterization experiments on 4H–SiC (0001) nitrogen-doped substrates implanted with different doses of xenon ions. Furthermore, unlike light ions such as hydrogen and helium, Xe ions cause significant damage to the inside of 4H–SiC, resulting in the inability to produce structurally complete silicon vacancy defects. Our findings provide insights into the fundamental mechanism of Xe-FIB processing and have implications for future applications in semiconductor technology.

Obtaining of thin films of manganese silicides on a Si surface by the method of solid-phase deposition and investigation of their electronic structure

The regularities of the formation of thin Mn/Si (111) nanofilms during solid-phase deposition of Mn on Si under conditions of ultrahigh vacuum ([Formula: see text][Formula: see text]Pa) and thin Mn4Si7/Si (111) nanofilms during annealing of the Mn/Si system have been studied. It has been established that silicon atoms diffuse into the Mn film up to a thickness of [Formula: see text]–12 monolayers, and Mn in Si up to [Formula: see text]–10 monolayers, therefore, a transition layer of nonstoichiometric MnxSiy silicide is formed at the Mn–Si interface. After heating at [Formula: see text][Formula: see text]K, the higher manganese silicide (HMS) Mn4Si7 is formed. In particular, it was found that the bandgap of Mn4Si7is [Formula: see text][Formula: see text]eV, and the electron affinity is [Formula: see text][Formula: see text]eV and in the work, the optimal thermal diffusion conditions for the formation of stoichiometric Mn4Si7 silicide are determined. It is shown that at [Formula: see text][Formula: see text]K, a partial formation of a chemical bond between manganese and silicon atoms occurs. At 1100[Formula: see text]K, a thin Mn4Si7 film with a good stoichiometric composition is formed.

Influence of alkyl groups on the formation of softenable polysilsesquioxanes

Polysilsesquioxanes (PSQ) containing phenyl groups as substituents on the silicon atom can form transparent, hard and glassy materials at room temperature, which reversibly soften when heated above the glass transition temperature. Further increase in temperature leads to irreversible curing. With this property, polyphenylsilsesquioxanes can be assigned to the so-called melting gels. In contrast to the aromatic systems, polysilsesquioxanes with alkyl groups belonging to this class of materials are not known. To identify structural differences between aryl and alkyl systems, polyalkylsilsesquioxanes (RPSQs with R = methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, hexadecyl, and octadecyl) were synthesised by a solvent-free, acid-catalysed hydrolysis and condensation reaction of alkyltrimethoxysilanes followed by thermal treatment at 300 °C under N2 atmosphere. The influence of the alkyl chain length on the structure built and the thermally initiated further condensation reactions were investigated via NMR, FTIR, TGA, DSC, SEC, and XRD. Depending on the alkyl chain length, the formation of highly crosslinked, insoluble systems (Me-PrPSQ), low molecular weight oligosilsesquioxanes in the form of cages (Hex-DecPSQ) to semicrystalline, lamellar layers (Dodec-OctadecPSQ) were detected. A low degree of condensation, inhibition of self-assembly and preferentially intermolecular condensation reactions were found to be crucial factors in the melting gel formation.Graphical So called melting gels are usually prepared by acid-catalysed hydrolysis and condensation of aromatic trialkoxysilanes. The final materials show a thermoplastic and a thermoset temperature regime based on the stabilisation of silanol groups in the material. In this study we transferred the typical synthetic conditions to alkyltrialkoxysilanes with different alkyl chain lengths and obtained completely changed structures of the synthesised polyalkylsilsesquioxanes compared to their aromatic counterparts. Depending on the chain length, densely cross-linked solids, viscous gels with cage-like structure and waxes with a lamellar composition were formed. Moreover, missing stabilisation of the OH groups and self-assembly phenomena, which favour the cage and semicrystalline layer formation were detected in the resulting materials, which leads to the loss of the typical melting gel properties.

Improved selectivity and anti-aging ability for 6FDA type carbon molecular sieve membranes by mixing silicon from macro-phase separation to molecule doping

Good gas separation performance and anti-aging ability are important for the applications of carbon molecular sieve membrane (CMSM). In this work, silicon atoms in the form of siloxane-Cl are introduced into 6FDA-DABA type polyimide (PI) precursor membrane, and benzimidazoles (BI) is copolymerized into PI to effectively improve the compatibility between PI and siloxane-Cl. By varying the content of siloxane-Cl, the composite membrane changes from macro-phase separation to molecule level miscibility, which leads to the formation of silicon-rich interface layer and silicon molecule doping after high temperature pyrolysis, respectively. The residual silicon content in CMSM could be as high as 1 wt%. The high content silicon doped CMSM exhibits much improved H2 permeability retention degree (3617 Barrer of H2 permeability, 62% higher) and H2/CH4 selectivity (138, 51% higher) as compared to control CMSM after 45 days of physical aging. This work proves that the incorporation of silicon in CMSMs in proper forms could significantly improve their molecular sieving and anti-aging performances; a higher content of residual silicon and molecule level doping are highly desired. The heteroatom doping is expected to pave a new way for finely tuning the micro-structures of CMSMs and improving gas separation performances.

Topological variations in aluminum-silicon alloys through inoculation with alkali earth elements: A first-principles study

Aluminum-silicon is a simple binary eutectic system with limited solid solubility of aluminum in silicon. Hypoeutectic compositions of Al-Si are the basis of several alloys for aerospace and automotive industries. The eutectic phase mixture contains coarse plate-like silicon. Typically, alkaline earth elements such as strontium, calcium, and barium are added in minute quantities that produce a fibrous network of silicon to improve the fracture toughness. Here, we use first-principles calculations to understand the origin of these morphological variations and explain these through interatomic interactions between aluminum, silicon, and inoculant atoms. Our results show that silicon atoms cluster together and arrange themselves in a planar (100) configuration within the aluminum matrix. When strontium, calcium, or barium atoms are added to the system, these atoms prefer to be near the silicon clusters and change the planar morphology to a three-dimensional configuration with facets on (111) planes.

Preparation of Hierarchical Porous and Tunable Silicon Microenvironment SAPO-18 Sheets for Methanol-to-Olefins

In this study, hierarchically porous SAPO-18 catalysts with abundant intracrystalline mesopores were designed and fabricated with a cost-effective non-surfactant cationic surfactant (polydimethyldiallylammonium chloride, PDADMAC) as a pore-forming agent, morphology regulator, and silicon inducer by a one-step method. PDADMAC promoted the introduction of silicon atoms in the SAPO-18 framework, making the hierarchical porous SAPO-18 sheets present abundant optimized acidity. With the combination of porous structure and suitable acid density, the hierarchical porous SAPO-18 sheets exhibited a threefold improvement in catalytic lifetime and a 4% increase in ethylene and propylene selectivity during the methanol-to-olefin (MTO) reaction, compared with the conventional SAPO-18 zeolite.

Microstructural characterization and mechanical properties of 6061 aluminum alloy processed with short-time solid solution and aging treatment

In order to reduce the cost of hot stamping of aluminum alloys and develop high-strength aluminum alloy parts for light-weight car body, short-time solid solution (SS) followed by shot-time artificial aging process was implemented for 6061 aluminum alloy with salt bath furnace and silicone oil bath. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM-EDS) and high-resolution transmission electron microscope (HR-TEM) were used to characterize the microstructural evolution in details. The holding time for SS can be reduced by 80 % with short-time SS treatment because of the decreased vacancy generation energy and effective boundary areas. Peak aging can be obtained at 200 °C for only 60 min, and the microstructure was characterized by a lot amount of acicular nano-size β’’ phase in the coherent with matrix, while precipitate-free-zone (PFZ) also appeared along the grain boundaries. All tensile properties such as 327 MPa yield strength, 362 MPa tensile strength and 13.1 % elongation meet the 6061 T6-standard. The micro stress introduced by superheated degree along with short-time treatment should be attributed to the accelerated diffusion of magnesium and silicon atoms, which greatly affects the diffusion hermodynamics and kinetics, especially nearby the grain boundaries.

Efficient deep-blue luminescence based on dual-channel intra/intermolecular exciplexes

Highly efficient and stable blue organic light-emitting diodes (OLEDs) cannot be easily obtained simultaneously. In particular, the efficiency roll-off as a reference index to evaluate the lifetime of deep-blue OLED at high luminescence is still severe. A novel molecule (CzSiTrz) connected with carbazole and triazine fragments by a nonconjugated silicon atom is designed. An intramolecular charge transfer emission and intermolecular exciplex luminescence in the aggregated state are obtained, resulting in a dual-channel intra/intermolecular exciplex (DCIE) emission with fast and efficient reverse intersystem crossing (RISC). Deep-blue OLED with Commission Internationale de l'Eclairage (CIE) coordinates of (0.157, 0.076) and a record-high external quantum efficiency (EQE) of 20.35% at high luminance (5000 cd m-2) is accomplished. Simple molecular synthesis and device fabrication of this strategy give a unique approach to realizing high-performance deep-blue electroluminescence.

Surface activation of Si-based Schottky diodes by bacterial biosynthesized AgInSe2 trimetallic alloy nanoparticles with evidenced negative capacitance and enhanced electro-dielectric performance

Semiconductor surface activation aims to modify the surface characteristics of a semiconductor material, such as its work function, surface energy, and chemical composition to improve its electrical properties and enable efficient charge transport across the device. Here, AgInSe2 complex trimetallic alloy was utilized as an interfacial layer in Si-based Schottky diodes and served as a semiconductor surface activator. The alloy nanoparticles were produced by green bacterial biosynthesis for the first time in the literature. XRD and micro-Raman manifested a nanostructured polycrystalline nature of the alloy with rhombohedral AgInSe2 and cubic Ag crystal phases. From the electrical measurements, the diode with AgInSe2 interfacial layer showed superior electrical and dielectric characteristics compared to the pure diode at room temperature. The introduction of interlayer resulted in a smaller ideality factor, larger barrier height, higher rectification ratio, lower leakage current, and better dielectric properties compared to the pure diode. The diode also recorded a negative permittivity, up to a certain frequency, that could enhance its performance when integrated into electronic circuits. The evidenced negative capacitance and its possible benefits in Schottky diodes are elaborated. The electro-dielectric enhancement was attributed to AgInSe2-induced semiconductor surface activation through the stimulation of the unpaired reactive silicon atoms at the semiconductor surface.

Synthesis and photophysical properties of cyclosiloxanes with substituted naphthyl groups

Cyclosiloxanes bearing 1-naphthyl and 5-substituted naphthyl groups have been prepared from the corresponding silanediols with bases such as triethylamine and 1,8-diazabicyclo[5.4.0]undec-7ene (DBU) in moderate yields. The selectivity for the synthesis of cyclotrisiloxanes [-SiAr2-O-]3 and cyclotetrasiloxanes [-SiAr2-O-]4 can be controlled by the substituents on the naphthyl rings and the strength of the base. A less reactive silanediol by introducing of electron-donating groups such as dimethylamino groups gave kinetically controlled cyclotrisiloxane. Di(1-naphthyl)silanediol was also found to give the corresponding cyclotrisiloxane with triethylamine. Meanwhile, reactive silanediol bearing electron-withdrawing groups afforded the corresponding thermodynamically stable cyclotetrasiloxane even in the presence of triethylamine. Strong base such as DBU promoted the rearrangement from cyclotrisiloxane to cyclotetrasiloxane by HPLC analysis, therefore the latter product was obtained as the main product. The photophysical properties of cyclotrisiloxanes 4b (Ar = 1-naphthyl) and 4c (Ar = 1-(5-N,N-dimethylaminonaphthlyl)), and cyclotetrasiloxanes 5a (Ar = 1-(5-cyanonaphthyl)) and 5b (Ar = 1-naphthyl) were carried out in different organic solvents. Cyclotrisiloxane 4b showed both monomer and excimer emission. Cyclotetrasiloxanes 5a and 5b showed characteristic excimer emission due to the fully overlapping naphthyl groups on the vicinal silicon atoms in the ground state from X-ray and theoretical calculations. Cyclotrisiloxane 4c showed broad emission and high quantum yield. The emission wavelength depended on the solvent polarity due to the ICT of the naphthyl groups. The solubility of the cyclosiloxanes was improved compared to previously reported cyclosiloxanes having 1-pyrenyl groups.

Influence of the Duration and Temperature of the Al-Fin Process for the Cast Iron Insert on the Microstructure of the Bimetallic Joint Obtained in the Piston Casting Process

The aim of this work was to determine the effect of the duration and temperature of the Al-Fin process for casting the bimetallic joint on the formation of the metallurgical bond between the AlSi9 aluminium alloy piston and the cast iron insert. Knowledge about the formation of individual bonding layers has a direct impact on the bonding strength between the aluminium alloy and the EN-GJLA-XNiCuCr15-6-2 austenitic cast iron ring. In the performed tests, the Al-Fin casting process was carried out for different temperatures of the liquid AlSi9 alloy. The temperature of the AlSi9 aluminium alloy varied in the range 700–950 °C in steps of 50 °C. The duration of the Al-Fin process ranged from 1 to 10 min. An optical microscope and a scanning electron microscope were used to study the microstructure of the bimetallic joints. The analysis of the microstructure of the bimetallic bond showed that characteristic layers are formed between the aluminium alloy piston and the cast iron insert: a transition layer, in which iron and aluminium atoms from both joined materials are mixed, and a diffusion layer, in which aluminium and silicon atoms penetrate the surface layer of the joined metals. The thickness of the intermetallic diffusion layer formed between the aluminium alloy and the cast iron insert is thinner and does not depend on the heating time of the aluminium insert in the bath. However, there is a significant effect of both the annealing time and the temperature of the AlSi9 aluminium alloy on the thickness of the transition zone.

Sistem Switching pada Automactic Transfer Switch (ATS) menggunakan Arduino UNO

Panel is a form of alternative energy that is widely used by humans today to be managed into electrical energy. Solar panels are made of semiconductor materials, especially silicon which is coated by a special additive. When sunlight approaches the cell, the electrons will be released from the silicon atoms and flow to form an electrical circuit so that electrical energy can be generated. The results of the study, where the transfer or switching carried out by the relay was orderead by the coding of the arduino uno. At the time before the transfer of switching, the arduino uno will delay a few seconds before switching the source. Where this ATS perfomance is controlled throught a magnetic force from an oen condition to a closed condition. As abreaker and a power connector, this tool has a material in the from of connecting contact point has a large size so that it can distribute large power loads. Then the contact point has a large size so that it can distribute large electric currents, one example of a type of breaker and connector ia an AC and DC relay as an automatic regulating device. From the results of the analysis it is concluded that the Switching Automatic Transfer Switch work process can be carried out by the relay on the order of the coding from Arduino UNO automatically