Co-deposition Of Silicon Research Articles

Biochar application enhanced rice biomass production and lodging resistance via promoting co-deposition of silica with hemicellulose and lignin

Biochar, an environmentally friendly soil amendment, is created via a series of thermochemical processes from carbon-rich organic matter. The biochar addition enhances soil characteristics dramatically and increases crop growth and yields. However, the mechanism by which biochar improves plant lodging resistance, which is heavily influenced by cell walls, remains unknown. Three rice cultivars were grown in an experimental field provided with four concentrations of biochar (10, 20, 30, 40 t ha−1). The biochar application enhanced biomass production and lodging resistance in all three cultivars by up to 29 % and 22 %, respectively, with the largest improvement at a biochar application rate of 30 t ha−1. Biochar application significantly enhanced stem cell wall-related characteristics, with an increase in stem breaking force, wall thickness, and plumpness of 52 %, 32 %, and 21 %, respectively, which are suggested to be major contributors to enhanced lodging resistance and biomass yield. Notably, cell wall composition and silica content analysis indicated a significant increase in hemicellulose, lignin, and silica content in biochar-treated samples up to 36 %, 13 %, and 58 %, respectively, when compared to plants not treated with biochar. Integrative analysis suggested that silica, hemicellulose, and lignin were co-deposited in cell walls, which influenced biomass production and lodging resistance. Furthermore, the transcriptome profile revealed that biochar application increased the expression of genes involved in biomass production, cell wall formation, and silica deposition. This study suggests that biochar application might improve both biomass production and lodging resistance by promoting the co-deposition of silicon with hemicellulose and lignin in cell walls.

ФОРМИРОВАНИЕ КАРБИДОКРЕМНИЕВЫХ ПОКРЫТИЙ МЕТОДОМ ХИМИЧЕСКОГО ГАЗОФАЗНОГО ОСАЖДЕНИЯ (обзор). Часть 2

The article provides an overview of the scientific and technical literature in the field of the formation of silicon carbide coatings by chemical vapor deposition (CVD). CVD is a complex process, approaches to which vary depending on the tasks being solved. Depending on the technological parameters it is possible to achieve both the deposition of pure silicon carbide and the co-deposition of silicon and carbon, mixed coating In the article attention is paid to the study of CVD from the point of view of the kinetic and parameters for deposition and thermodynamic.

ФОРМИРОВАНИЕ КАРБИДОКРЕМНИЕВЫХ ПОКРЫТИЙ МЕТОДОМ ХИМИЧЕСКОГО ГАЗОФАЗНОГО ОСАЖДЕНИЯ (обзор). Часть 1

The article provides an overview of the scientific and technical literature in the field of the formation of silicon carbide coatings by chemical vapor deposition (CVD). CVD is a complex process, approaches to which vary depending on the tasks being solved. Depending on the technological parameters, the initial reagents, the substrate for deposition, the type and design of the CVD reactors, it is possible to achieve both the deposition of pure silicon carbide and the co-deposition of silicon and/or carbon. In the first part of the article, attention is paid to the study of CVD from the point of view of the mechanisms of chemical reactions, the design of the deposition apparatus, the substrates for deposition.

Deposition and etching behaviour of boron trichloride gas at silicon surface

The deposition and etching at a silicon surface by boron trichloride gas were overviewed in a wide temperature range using a chemical vapour deposition reactor. At temperatures lower than 800 °C, while the silicon surface was covered with boron, the formed film thickness was ignorable. At 900 °C, the boron deposition rate increased to 0.25 μm min−1. In the temperature range between 900 and 1000 °C, the boron film formation was considerable. In contrast, at 1100 °C, the silicon surface was etched at 0.36 μm min−1. At temperatures higher than 1050 °C, while etching occurred along with producing chlorosilanes, the silicon surface after the etching was still covered with boron. Boron deposition and silicon etching might simultaneously occur at high temperatures by the boron trichloride gas. By adjusting the surface temperature to 800 °C, boron and silicon co-deposition was possible using the gas mixture of dichlorosilane and boron trichloride.

Co-deposition of silicon with rare earth elements (REEs) and aluminium in the fern Dicranopteris linearis from China

Dicranopteris linearis is a fern that accumulates unusually high concentrations (up to 0.3% dry weight) of rare earth elements (REEs) in China. Previously, we reported that D. linearis accumulates high concentrations of aluminium (Al) and silicon (Si) in the fronds, but the interactions between these elements and REEs were unknown. In this study, a range of analytical techniques, including chemical extractions, Scanning-Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were used to study the association of REEs with Al and Si. The results show that D. linearis accumulates high concentrations of REEs (up to 3830 mg kg−1), Al (up to 9660 mg kg−1) and Si (up to 20,300 mg kg−1), with concentrations increasing with age and frond order of pinna. The extraction patterns suggest the existence of REEs-Si and Al-Si complexes. The SEM-EDS analysis confirmed the existence of phytoliths (Al) deposits in the protoplast and apoplast of the pinna cells. The upper epidermis of the pinnule and the pericycle of the midvein are more concentrated in phytoliths (Al) particles. The LA-ICP-MS analysis revealed that REEs and Al are preferentially compartmentalized within bio-inactive tissues of the pinnules, e.g. necrotic tissues (REEs) and in the margins (Al). Co-deposition of Si with REEs and Al may be a mechanism for dealing with the high concentrations of REEs and Al in D. linearis fronds.

High-stability transparent amorphous oxide TFT with a silicon-doped back-channel layer

We significantly reduced various electrical instabilities of amorphous indium gallium zinc oxide thin-film transistors (TFTs) by using the co-deposition of silicon on an a-IGZO back channel. This process showed improved stability of the threshold voltage (Vth) under high temperature and humidity and negative gate-bias illumination stress (NBIS) without any reduction of IDS. The enhanced stability was achieved with silicon, which has higher metal-oxide bonding strengths than gallium does. Additionally, SiOX distributed on the a-IGZO surface reduced the adsorption and the desorption of H2O and O2. This process is applicable to the TFT manufacturing process with a variable sputtering target.

Subwavelength single layer absorption resonance antireflection coatings

We present theoretically derived design rules for an absorbing resonance antireflection coating for the spectral range of 100 - 400 nm, applied here on top of a molybdenum-silicon multilayer mirror (Mo/Si MLM) as commonly used in extreme ultraviolet lithography. The design rules for optimal suppression are found to be strongly dependent on the thickness and optical constants of the coating. For wavelengths below λ ∼ 230 nm, absorbing thin films can be used to generate an additional phase shift and complement the propagational phase shift, enabling full suppression already with film thicknesses far below the quarter-wave limit. Above λ ∼ 230 nm, minimal absorption (k < 0.2) is necessary for low reflectance and the minimum required layer thickness increases with increasing wavelength slowly converging towards the quarter-wave limit.As a proof of principle, SixCyNz thin films were deposited that exhibit optical constants close to the design rules for suppression around 285 nm. The thin films were deposited by electron beam co-deposition of silicon and carbon, with N+ ion implantation during growth and analyzed with variable angle spectroscopic ellipsometry to characterize the optical constants. We report a reduction of reflectance at λ = 285 nm, from 58% to 0.3% for a Mo/Si MLM coated with a 20 nm thin film of Si0.52C0.16N0.29.

Low-activity aluminide coatings for superalloys using a slurry process free of halide activators and chromates

Slurry aluminide coatings have been well known for a number of years and are widely used to protect metallic surfaces from oxidation and corrosion. A variety of commercial slurries is available to aluminize the surfaces of nickel-based superalloys, however, they have several disadvantages. They contain environmentally harmful substances such as chromates or halides which are used as binders or to activate the diffusion species. Additionally, up to now slurry coatings were only used to produce precipitate-rich coatings, with a microstructure comparable to high aluminum activity coatings produced by chemical vapor deposition (CVD) like pack cementation.In this work these limitations have been overcome by carefully designing the powder composition of the slurry. Three different nickel-aluminide coatings were developed and applied onto CM-247 nickel-based alloy and Pt-diffused CM-247. By addition of chromium we achieved coatings with a similar microstructure and Al-content (of around 40at.%), comparable to the state of the art low-activity coatings produced by CVD. Co-deposition of silicon was also achieved in a single step, maintaining the low-activity structure by combining Al–Si powder and chromium. Furthermore, this coating procedure was combined with a platinum electrodeposition step in order to produce single phase Pt-modified low-activity aluminide coatings.

Aluminum and silicon co-deposition by the chemical vapor deposition in fluidized bed reactor technique as a precursor of protective coatings of mullite

Ceramic coatings are excellent candidates to protect metallic structures that operate at high temperature. Regarding these ceramic coatings, mullite is a good option, since it presents very good mechanical properties, great corrosion resistance, high thermal resistance and high durability. The chemical vapor deposition by fluidized bed reactor (CVD-FBR) is an interesting technique to create thin and adherent protective films on metallic surfaces. Furthermore, this method is cheap and easy to apply. The first step to obtain mullite coatings would be the co-deposition of aluminum and silicon coatings by CVD-FBR. Thermodynamic calculations were made before the experiments to study the system and optimize the working conditions. These depositions take place in a fluidized bed reactor and the base material used is a commercial AISI-304 stainless. This technique is based upon reaction among aluminum chloride (AlCl 3 (g)) and silicon chloride (SiCl 4 (g)). The optimization of the deposition conditions (deposition temperature, time, fluxes, etc.) is discussed. The analysis of the results is carried out by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). In addition, further oxidation of these precursor coatings is made in order to obtain the definitive system of a protective ceramic layer. Oxidation of the coated samples is made at different temperatures and times to obtain the best mullite structure.

Three-dimensional structures formed with C 60 and amorphous silicon––a feasibility study on the formation of a composite material

The co-deposition of silicon and C 60 leads to the formation of a composite material, where the concentration of the components can be controlled via the respective particle fluxes. Information on the composition and electronic properties of the thin layers is obtained by photoelectron spectroscopy in the ultraviolet (UPS) and X-ray regime (XPS), while transmission electron microscopy (TEM) was employed for selected samples. The C 60 cages remain intact upon deposition and are embedded in an amorphous silicon (a-Si) matrix. The interaction between the Si and C 60 leads to a shift of all C 60-related spectral features and pinning of the Fermi level at the internal C 60–a-Si heterojunction and the valence band offset (the energy difference between the valence band maxima of the two components) is about 1.0 eV. The electronic properties at the internal C 60–a-Si interface are equivalent to a 2D layer system and independent of the thin film composition. The composite material is highly stable up to a temperature of 700 °C, when the fullerenes break down and react completely with the a-Si matrix to form SiC. The presence of small SiC crystallites embedded in an a-Si matrix is confirmed with TEM.

Silicide Coatings for Niobium: Mechanisms of Chromium and Silicon Codeposition by Pack Cementation

In the present work, a pack cementation (PC) process was carried out to codeposit Cr and Si on a Nb substrate. Three masteralloy compositions (Cr 36.4 Si 63.6 (A), Cr 44.5 Si 55.5 (B) and Cr 14.3 Si 85.7 (C)) were tested in the presence or absence of an activator (CrCl 3 or SiCl 4 ). The study of deposition mechanisms was undertaken through thermodynamic and dynamic calculations. Si appears to be deposited due to disproportionation reactions of lower halides, SiCl 2 and SiCl 3 , while Cr seems to be transported by a molecular species containing Cr and Si, not yet identified.

MBE Si regrowth on carbon-induced Si(001)-c(4×4) reconstructions studied by RHEED

Si(001)-c(4×4) surfaces are obtained by exposing Si(001)-2×1 surfaces at 600°C to ethylene doses that determine C coverages in the submonolayer range. This reconstruction reveals a carbon enrichment of the topmost silicon layers. As the c(4×4) reflection high energy electron diffraction pattern can be maintained in spite of rather thick Si regrowth layers, we can conclude that this C derm is able to float at the surface during the Si capping. This segregation process is strongly dependent on the growth mode. As identified by RHEED intensity oscillations, a Si step flow growth is necessary to allow carbon to float in the first four silicon top-layers. An interplay is found between the kinetic growth conditions leading to this C-segregation and those of a self-organization process of C-rich clusters that we have observed in the course of Si 1− y C y alloy growth obtained by codeposition of silicon and carbon.

A new 30°-rotated (7×7) superstructure formed by codeposition of Cu and Si on Si(111) (7×7)

An unusual (7×7)R30° reconstruction caused by copper and silicon codeposition on Si(111) (7×7) at between 240 and 300°C was observed with high-resolution low-energy electron diffraction (HRLEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy (AES). The HRLEED measurements of the deposited film showed six widened first-order superlattice beams with a separation consistent with that of the Si (7×7) reconstruction, and clearly inconsistent with the well-documented incommensurate “5×5” structure. The (7×7) reconstruction of the initial Si(111) surface, though, was completely absent from the HRLEED pattern of the deposited surface. STM measurements of the deposited film showed a structure with about five to ten exposed layers, terraces on the order of 50 to 100 nm across, and pits at least 2 nm deep and on the order of 10 nm across. The pits likely resulted from Cu decoration of the film defects. The atomic-resolution images showed a loose hexagonal array of superstructures, with observable rotations (17°) with respect to one another and with some clustering of atoms within the superstructure. AES measurements indicated that the surface chemical composition was largely Si, with 9±4% Cu. The wide range of observed in-plane domain orientations was likely the result of thermally activated nucleation within the terraces.

Heteroepitaxial growth of 3C-SiC on (100) silicon by C 60 and Si molecular beam epitaxy

Thin, hydrogen-free 3C-SiC films were grown on (001) silicon substrates at rather low temperatures by C 60-carbonization under simultaneous silicon co-deposition at different rates. Fullerene molecules and silicon were evaporated from Knudsen cells. The dependence of the structure and phase composition on Si rate and working pressure has been examined. Optimum growth conditions for the resulting SiC films are examined. Elastic recoil detection analysis spectra show the formation of a stoichiometric SiC layer under all conditions applied. X-Ray diffraction measurements reveal that the resulting 3C-SiC films, obtained under optimized conditions, are free of twin structures and epitaxially aligned to the underlying silicon substrate. Cross-section transmission electron microscopy confirms a significant structural improvement as Si is co-deposited. For samples formed without Si co-deposition, pits of pyramidal shape were found in the silicon substrate near the SiC/Si interface by scanning electron microscopy. Silicon co-evaporation during carbonization leads to a significant reduction of the pit size.

Structure and stability of cobalt-silicon-germanium thin films

The phase formation and stability of CoSi 2 on strained epitaxial Si 0.80Ge 0.20 Si (0 0 1) thin films has been investigated. Silicide films prepared via direct deposition of cobalt ( Co SiGe ), and via co-deposition of silicon and cobalt ( Co+ 2Si SiGe ), were compared. EXAFS, XRD, and sheet-resistance measurements indicated that co-deposited Co+2Si films annealed at 400–700°C exhibit the expected low-resistivity CoSi 2 structure but were susceptible to roughening, pinhole formation, and agglomeration. In contrast, the Co SiGe structure formed CoSi 2 only after annealing at 700°C and silicide formation was accompanied by Ge segregation in the contact region. In situ RHEED experiments indicated that growth of CoSi 2 co-deposited on SiGe at 400–500°C results in immediate island formation. Template methods, which are often used to enhance the quality of co-deposited Co+ 2Si Si structures, did not lead to two-dimensional growth in the Co+ 2Si SiGe system. In situ EXAFS measurements of 2 Å Co films deposited on SiGe substrates and annealed at 450°C suggested that the failure to achieve two-dimensional growth may be due to preferential bonding of Co to Si atoms at the interface, which prevents the formation of a continuous CoSi 2 template.

Thin Films of CoSi2 Co-Deposited onto Si1-xGexAlloys

AbstractCobalt disilicide films have been formed on strained epitaxial Si0.80Ge0.20/Si(100) alloys via co-deposition of silicon and cobalt. Co-deposition is shown to improve the epitaxy and prevent the phase segregation commonly observed with the formation of Co/SiGe contacts using other methods such as the direct deposition of cobalt onto SiGe or the sequential deposition of a silicon sacrificial layer and cobalt onto SiGe. EXAFS measurements at the cobalt K edge indicate that co-deposited films annealed at 500–700° C are indeed crystalline CoSi2 throughout this temperature range. The XRD patterns of the co-deposited films do not exhibit any of the CoSi2 (111), (220) or (311) peaks normally associated with other preparation methods. The sheet resistance and r.m.s. roughness of the CoSi2 films increase monotonically with annealing temperature. These results indicate that co-deposited films are epitaxial to the (100)-oriented SiGe substrate and suggest that low thermal budget, low resistivity contacts to strained SiGe can be grown with this method. Issues related to the presence of Ge at the CoSi2/substrate interface will be discussed.

Allotaxial growth of epitaxial Si/FeSi 2/Si heterostructures

We fabricated Si/FeSi 2/Si(111) heterostructures by a new method, called molecular beam allotaxy (MBA). Codeposition of silicon and iron at temperatures around 650°C leads to the formation of FeSi 2 precipitates in the crystalline silicon matrix. The subsequent annealing was performed in two steps. First annealing at temperatures in the range 1150–1170°C resulting in the formation of high quality buried epitaxial metallic α-FeSi 2 layers with a minimum yield value of X min = 12%. Cross section transmission electron micrographs (XTEM) reveal these films to be continuous with sharp interfaces. The lowest resistivity for α-FeSi 2 was ϱ = 225 μΩ·cm at room temperature. By a second anneal at temperatures below the phase transition temperature the metallic α-FeSi 2 was transformed to the semiconducting β-FeSi 2. These first results prove the applicability of MBA for the growth of metallic and semiconducting FeSi 2 layers in Si.

Dependences of titanium silicide properties on the ratio of silicon to titanium used for electron-beam coevaporation onto heated substrates

Variations of the properties of titanium silicides prepared under various deposition conditions were investigated. An amorphous phase was observed to form when samples were prepared by codeposition of silicon and titanium at the substrate temperature T s of 120°C. However, it was found that considerable crystallization takes place at T s = 300° C, even though island-like amorphous regions are present at the silicide-silicon substrate interface. The film properties of samples prepared at relatively high T s were observed to change with the deposition conditions in a systematic manner. It was suggested that the amorphous phase is probably the first product of the intermixing even at elevated substrate temperatures. It was also postulated that the silicide formation process may involve evaporation of the amorphous phase. Thus, the film properties were said to be determined by silicon diffusion from the substrate, and crystallization as well as evaporation of the amorphous phase. Each of these mechanisms becomes dominant depending on the initial composition used for codeposition. This conjecture was shown to be successful in explaining the observed variations of properties such as voids, silicon precipitates, interface roughness, and resistivity.

Titanium silicide contacts on semiconducting diamond substrates

Titanium silicide contacts have been deposited on semiconducting (p-type) natural diamond substrates by the codeposition of silicon and titanium by electron-beam evaporation. Current-voltage (I–V) measurements conducted at room temperature have demonstrated rectifying characteristics. Consistent with the observed small turn-on voltage, the corresponding I–V measurements recorded at 400°C exhibit ohmic-like behaviour. However, on subsequent annealing of the titanium silicide contacts at 1100°C in a vacuum of ∼10−6 Torr for 30min, stable rectifying I–V characteristics were observed in the 25–400°C temperature range.

Si/SiOx/Si hole-barrier fabrication for bipolar transistors using molecular beam deposition

Abstract SiOx layers were deposited on silicon substrates in a silicon MBE system by co-deposition of silicon and oxygen. The oxygen concentration increased as the deposition temperature decreased. Oxygen pressure was 5×10−5 Torr and the silicon deposition rate was 0.2 A s−1. Composition was determined by using X-ray photoelectron spectroscopy and Auger electron spectroscopy, and the electric properties of its metal-oxide-semiconductor capacitor were measured. The growth procedure used here offers high controllability in the thickness of the deposited SiOx layer and permits subsequent silicon growth in the same silicon MBE chamber. Such Si/SiOx/Si structures, which may be applied to the hole-barrier between the base and emitter layers in bipolar transistors, were also successfully grown using this method. We fabricated this type of bipolar transistor and one order higher current gain than that of usual polysilicon emitter was obtained when SiOx layer thickness was 20 A.