Effect of Thermal Annealing on Characteristics of Polycrystalline Silicon

Oxygen and carbon behaviors and minority-carrier lifetimes in multi-crystalline silicon （mc-Si） used for solar cells are investigated by FTIR and QSSPCD before and after annealing at 750～ 1150℃ in N2 and O2 ambient. For comparison, the annealing of CZ silicon with nearly the same oxygen and carbon concentrations is also carried out under the same conditions. The results reveal that the oxygen and carbon concentrations of mc-Si and CZ-Si have a lesser decrease,which means oxygen precipitates are not generated,and grain boundaries in mc-Si do not affect carbon behavior. Bulk lifetime of mc-Si increases in N2 and O2 ambient at 850,950,and 1150℃ ,and the lifetime of mc-Si wafers annealed in 02 are higher than those annealed in N2, which shows that a lot of impurities in mc-Si at high temperature annealing diffuse to grain boundaries,greatly reducing recombination centers. Interstitial Si atoms filling vacancies or recombination centers increases lifetime.

Silicon Mitigates Aluminum Toxicity of Tartary Buckwheat by Regulating Antioxidant Systems

Aluminum (Al) toxicity is a considerable factor limiting crop yield and biomass in acidic soil. Tartary buckwheatgrowing in acidic soil may suffer from Al poisoning. Here, we investigated the influence of Al stress on the growthof tartary buckwheat seedling roots, and the alleviation of Al stress by silicon (Si), as has been demonstrated inmany crops. Under Al stress, root growth (total root length, primary root length, root tips, root surface area, androot volume) was significantly inhibited, and Al and malondialdehyde (MDA) accumulated in the root tips. At thesame time, catalase (CAT) and ascorbate peroxidase activities, polyphenols, flavonoids, and 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free-radical scavenging abilitywere significantly decreased. After the application of Si, root growth, Al accumulation, and oxidative damage wereimproved. Compared to Al-treated seedlings, the contents of ·O2− and MDA decreased by 29.39% and 25.22%,respectively. This was associated with Si-induced increases in peroxidase and CAT enzyme activity, flavonoidcompounds, and free-radical scavenging (DPPH and ABTS). The application of Si therefore has positive effectson Al toxicity in tartary buckwheat roots by reducing Al accumulation in the roots and maintaining oxidationhomeostasis.

Analysis of oxide layer structure in nitrided grain-oriented silicon steel

The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method.Due to the additional nitriding process,a high nitrogen content exists in the oxide layer,which changes the structure of the oxide layer.In this study,the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),glow discharge spectrometry(GDS),and X-ray diffraction(XRD).The size and orientation of ferritic grains in the oxide layer were characterized,and the distribution characteristics of the key elements along the thickness direction were determined.The results show that the oxide layer of the steel sample mainly comprised particles of Fe2SiO4 and spherical and lamellar SiO2,and Fe4N and fcc-Fe phases were also detected.Moreover,the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer;however,some ferritic grains exhibited same orientations as those in the neighboring matrix.Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer.The form of nitrogen enrichment in the oxide layer was analyzed,and the growth mechanism of ferritic grains during the oxide layer formation is proposed.

Effect of Boundary Layers on Polycrystalline Silicon Chemical Vapor Deposition in a Trichlorosilane and Hydrogen System

This paper presents the numerical investigation of the effects of momentum, thermal and species boundary layers on the characteristics of polycrystalline silicon deposition by comparing the deposition rates in three chemical vapor deposition （CVD） reactors. A two-dimensional model for the gas flow, heat transfer, and mass transfer was coupled to the gas-phase reaction and surface reaction mechanism for the deposition of polycrystalline silicon from trichlorosilane （TCS）-hydrogen system. The model was verified by comparing the simulated growth rate with the experimental and numerical data in the open literature. Computed results in the reactors indicate that the deposition characteristics are closely related to the momentum, thermal and mass boundary layer thickness. To yield higher deposition rate, there should be higher concentration of TCS gas on the substrate, and there should also be thinner boundary layer of HCl gas so that HCl gas could be pushed away from the surface of the substrate immediately.

Studies on the polycrystalline silicon/SiO2 stack as front surface field for IBC solar cells by two-dimensional simulations

Interdigitated back contact（IBC） solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO_2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO_2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO_2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm.Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.

Effect of Incidence Angle of Magnetic Field on the Performance of a Polycrystalline Silicon Solar Cell under Multispectral Illumination

The aim of this work is to investigate, with a three-dimensional steady-state approach, the effect of the incidence angle of a magnetic field on the performance of a polycrystalline silicon solar cell under multispectral illumination. The magneto-transport and continuity equations of excess minority carriers are solved to find the expression of the density of excess minority carriers and the related electrical parameters, such as the photocurrent density, the photovoltage and the electric power, of a grain of the polycrystalline silicon solar cell. The influence of the incidence angle of the magnetic field on the diffusion coefficient, the short-circuit photocurrent density, the open-circuit photovoltage and the electric power-photovoltage is studied. Then, the curves of the electric power-photovoltage is used to find the maximum electric power allowing to calculate, according to the incidence angle of the magnetic field, the fill factor and the conversion efficiency. The study has shown that the increase of the incidence angle of the magnetic field from 0 rad to π/2 rad, can reduce the degradation of the performance of solar cells.

Carrier Transport Across Grain Boundaries in Polycrystalline Silicon Thin Film Transistors

We established a model for investigating polycrystalline silicon（poly-Si） thin film transistors（TFTs）.The effect of grain boundaries（GBs） on the transfer characteristics of TFT was analyzed by considering the number and the width of grain boundaries in the channel region,and the dominant transport mechanism of carrier across grain boundaries was subsequently determined.It is shown that the thermionic emission（TE） is dominant in the subthreshold operating region of TFT regardless of the number and the width of grain boundary.To a poly-Si TFT model with a 1 nm-width grain boundary,in the linear region,thermionic emission is similar to that of tunneling（TU）,however,with increasing grain boundary width and number,tunneling becomes dominant.

Multifunctional silicon-based light emitting device in standard complementary metal oxide semiconductor technology

A three-terminal silicon-based light emitting device is proposed and fabricated in standard 0.35 μm complementary metal-oxide-semiconductor technology. This device is capable of versatile working modes： it can emit visible to near infra-red （NIR） light （the spectrum ranges from 500 nm to 1000 nm） in reverse bias avalanche breakdown mode with working voltage between 8.35 V-12 V and emit NIR light （the spectrum ranges from 900 nm to 1300 nm） in the forward injection mode with working voltage below 2 V. An apparent modulation effect on the light intensity from the polysilicon gate is observed in the forward injection mode. Furthermore, when the gate oxide is broken down, NIR light is emitted from the polysilicon/oxide/silicon structure. Optoelectronic characteristics of the device working in different modes are measured and compared. The mechanisms behind these different emissions are explored.

4H-SiC Schottky barrier diodes with semi-insulating polycrystalline silicon field plate termination

Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The relative dielectric con-stant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leak-age current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.

Photoluminescence and Electroluminescence Studies on Tb-Doped Silicon Rich Oxide Materials and Devices

Photoluminescence （PL） characteristics of Tb-doped silicon rich oxide （SRO） films prepared by DC-sputtering and post-annealing processes were studied. The silicon richness of the SRO film could be controlled by varying the sputtering power and oxygen concentration in the sputtering chamber. PL emission from the as-deposited sample was found to be composed of Th^3 ＋ intra 4f transition-related emission and the silicon nano particle-related broad bandwidth emission. Thermal annealing could significantly improve the material properties as well as the PL signals. PL properties depended strongly upon the annealing scheme and silicon richness. Annealing at high temperatures （900- 1050℃） enhanced Tbrelated emission and suppressed the silicon nano particle-related emission. For samples with different silicon richness, annealing at 950 ℃ was found to produce higher PL signals than at other temperatures. It was attributed more to lifetime quenching than to concentration quenching. Electroluminescent （EL） devices with a capacitor structure were fabricated, the optimized process condition for the EL device was found to be different from that of PL emission. Among the annealing schemes that were used, wet oxidation was found to improve device performance the most, whereas, dry oxidation was found to improve material property the most. Wet oxidation allowed the breakdown electrical field to increase significantly and to reach above 10 mV·cm^-1. The EL spectra showed a typical Th^3＋ emission, agreeing well with the PL spectra. The I-V measurements indicated that for 100 nm thick film, the Fowler-Nordheim tunneling started at an electrical field of around 6 mV·cm^-1 and the light emission became detectable at a current density of around 10-4 A·cm^-2 and higher. Strong electroluminescence light emission was detected when the electrical field was close to 10 mV·cm^-1.

Nafion/Silicon Oxide Composite Membrane for High Temperature Proton Exchange Membrane Fuel Cell

Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate （TEOS） in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nation membrane and the thermo stability of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. Furthermore, the tensile strength of Nation/Silicon oxide composite membrane is similar to that of the Nation membrane. The proton conductivity of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. When the Nation/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC, a higher current density value （1 000 mA/cm^2 at 0.38 V） than that of the Nafion1135 membrane （100 mA/cm^2 at 0.04 V） was obtained at 110 ℃.

Optical and Electrical Properties of Hydrogenated Silicon Oxide Thin Films Deposited by PECVD

In this work, n-type amorphous silicon oxide thin films were deposited by RF-PECVD method using a gas mixture of SiH4, CO2, H2, and PHy The deposition rate, refractive index, band gap, crystalline volume fraction, and conductivity of the silicon oxide thin films were determined and analyzed. The film with refractive index of 1.99, band gap of 2.6eV and conductivity of 10-7 S/cm was obtained, which was suitable for the intermediate reflector layer.

Oxidation Kinetics of (111) Silicon Monocrystal and Morphology of Oxide Film in Dry Oxygen Atmosphere

1. Introduction Thermal oxidation of silicon monocrystalis a very important process in fabricationof metal--oxide--semiconductor (MOS) devices.In recent years it has received great atten-tion. Various proposals for oxidation modeshave been made by different groups.Now most of the authors working in thisfield hold the view that the oxidation rateof silicon obeys a typical parabolic rule,that is, the oxidation reaction is controlledby diffusion. The experimental data inRef. can be taken and a kinetic curve

Direct Determination of Trace Silicon in Lanthanum Oxide by Using a Selective Volatility and Slurry Sampling-FETV-ICP-AES

A new method for determination of trace silicon in high purity lanthanum oxide by using electrothermal vaporization (ETV) ICP AES with polytetrafluoroethylene(PTFE) slurry as a fluorinating reagent has been proposed. Under the optimized experimental conditions, the fluorination reactions of analyte(Si) and matrix(La) with PTFE in the graphite furnace took place at high temperature, and the fractional volatilily between Si and La was observed. Based on this principle the matrix interference could be eliminated. The detection limit of Si was 4.0 μg·L -1 , and the RSD was 3.4%( C =0.2 mg·L -1 , n =10). The procedure proposed has been applied successfully to determine trace Si in La 2O 3 without any chemical pre treatment.

Study of Thermal Treatment on Properties of Polycrystalline Silicon

The effects of thermal annealing on oxygen behavior and carrier lifetimes of mc-Si wafers were investigated by means of FTIR and QSSPCD during single step and two step heat treatments in N2 and O2 ambient. It reveals that interstitial oxygen concentration of mc-Si and CZ-Si has a slighter decrease in N2 and O2 ambient during single-step annealing, which means oxygen precipitates are not generated. But oxygen concentration greatly decreases and generates a number of oxygen precipitates during two-step annealing. Bulk lifetime of mc-Si increases in N2 ambient at 850, 950, 1150 ℃ respectively, and annealing in O2 shows better results than that in N2 and annealing in two-step reflected better consequence than annealing in single-step. But lifetime of CZ-Si annealed in N2 or O2 decreases rapidly. The reason of lifetime increase is probably considered due to the fact that interstitial Si atoms of Si/SiO2 interface fill vacancies or some recombination centers at high temperature annealing. Moreover, a number of impurities in mc-Si probably diffuse to grain boundaries so that greatly reduce recombination centers result to lifetime rising.

High Performance Silicon Nitride-based Composite Materials with Rare-earth Oxides Additives

In the present paper,a silicon nitride-based composite processed with rare-earth oxidesadditives is presented.Its bend strength can be maintained at a value as high as 1000 MPafrom 1000 to 1370℃ and the fracture toughness measures 9-10 MPa·m1/2.The static fa-tigue behavior at 1370℃ of this material is also encouraging.Besides,two another α′/β′sialon composites doped with rare-earth oxides are also described.The effects of processingparameters on the microstructure and the properties of the materials are discussed in somedetails.

Low Energy H^+ Effects on the Photovoltaic and Optical Properties of Polycrystalline Silicon Solar Cells

Low energy hydrogen ion was used to passivate the electrically active defects existing in grains and grain boundaries of polycrystalline silicon solar cells.Short circuit current of H + implanted cells remarkably increased before and after preparing TiO 2AR(antireflective)coating.The measurements(at λ=6328) of the optical properties of H + implanted silicon samples show that:the value of absorption coefficient reached the level of a Si;refractive index n and reflectivity R significantly decreased;the optical band gap increased from 1.1 eV to 1.3 eV.The results indicate that Si H bonds have been formed after H + implantation.The calculation shows that the optical thickness cycle of TiO 2 AR coating will reduce correspondingly in order to obtain the optimum optical match between AR coating and implanted silicon since refractive index decreases after H + implantation.

Magnetic properties of oxides and silicon single crystals

The magnetic properties of single crystals Si,Sr Ti O_(3),La Al O_(3),Mg O,and(La,Sr)(Al,Ta)O_(3)were investigated systematically.Three origins of the magnetizations of these crystals,namely,an intrinsic diamagnetic,a paramagnetic,and a ferromagnetic contribution,have been found to influence the magnetic signals measured on the crystals,in some important application scenarios such crystals being served as substrates with the magnetic thin film epitaxially grown on.Quantitative analyses methodologies were developed and thorough investigations were performed on the crystals with the intrinsic materials parameters thus revealed,especially that the intrinsic diamagnetic susceptibility differential dχdia/d T were identified quantitatively for the first time in Sr Ti O_(3),La Al O_(3),Mg O,and(La,Sr)(Al,Ta)O_(3).The paramagnetic contribution is found to be the key in terms of the magnetic properties of the crystals,which in turn is in fact a consequence of the 3d impurities doping inside the crystal.All the intrinsic materials parameters are given in this paper as datasets,the datasets are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00028.

Polycrystalline Silicon Solar Cell p-n Junction Capacitance Behavior Modelling under an Integrated External Electrical Field Source in Solar Cell System

The state of the p-n junction is very important to explain the performances of a solar cell. Some works give the influence of the electric field on the junction capacitance. However, these works do not relate the quality of the p-n junction under the electic field. The present manuscript is about a theoretical modelling of the p-n junction capacitance behavior of the polycrystalline silicon solar cell under an integration of the external electrical field source. An external electrical source is integrated in a solar cell system. The electronic carriers charge generated in the solar cell crossed mainly the junction with the great strength external electrical field. In open circuit, this crossing of the electronic charge carriers causes the thermal heating of the p-n junction by Joule effect. The p-n junction capacitance plotted versus the junction dynamic velocity and the photo-voltage for different external electrical fields. The electric field causes the decrease of the photo-voltage mainly the open-circuit photo-voltage. The decrease of the photo-voltage translates the narrowing of the Space Charge Region (SCR). The average value of the external electric field used in this study is not sufficient to cause the breakdown of the p-n junction of the solar cell system under integration of the external electrical field production source. The increase of the electrical field causes rather the narrowing of the SCR. That can provide an improvement of the solar cell’s electrical outputs.

Ginseng ameliorates pulmonary toxicity induced by silicon dioxide nanoparticles in rats

Objective:To investigate the protective and therapeutic role of ginseng against silicon dioxide nanoparticles(SiO2NPs)-induced toxicity in the lungs.Methods:Sixty male rats were divided into five groups(n=12/group);group 1 was used as a control,group 2 received ginseng,group 3 was treated with SiO2NPs,and group 4 was pretreated with ginseng one week before SiO2NPs,while group 5 was given SiO2NPs one week before supplementation with ginseng.Animals were treated with both ginseng and SiO2NPs orally for five weeks.Real-time PCR was used to measure gene expression.Besides,DNA damage and cell cycle changes were determined by comet assay and flow cytometry,respectively.Histological study was also done to assess the effect of ginseng on SiO2NPs-induced toxicity.Results:SiO2NPs increased lipid peroxidation and decreased the activities of antioxidant enzymes.SiO2NPs induced apoptosis in lung tissues as revealed by upregulation of Bax and caspase 3 and downregulation of Bcl-2 as well as the induction of DNA damage.SiO2NPs also caused inflammation as indicated by upregulation of the inflammation-related genes[interleukin 1 beta(IL-1β),tumor necrosis factor-alpha(TNF-α),nuclear factor kappa B(NF-κB),cyclooxygenase 2(COX2),and transforming growth factor-beta 1(TGFβ1)]as well as cell cycle arrest in the G0/G1 phase of lung cells.Moreover,histopathological examination proved the biochemical and molecular perturbations that occurred due to SiO2NPs toxicity.However,ginseng alleviated SiO2NPs-induced toxicity in rat lung.Conclusions:Ginseng has a potent preventive and therapeutic effect and could be used in the treatment of SiO2NPs-induced pulmonary toxicity.