Silicon Deposition Research Articles

Copper Silicide Nanowires as Hosts for Amorphous Si Deposition as a Route to Produce High Capacity Lithium-Ion Battery Anodes.

Herein, copper silicide (Cu15Si4) nanowires (NWs) grown in high densities from a metallic Cu substrate are utilized as nanostructured hosts for amorphous silicon (aSi) deposition. The conductive Cu15Si4 NW scaffolds offer an increased surface area, versus planar substrates, and enable the preparation of high capacity Li-ion anodes consisting of a nanostructured active material. The formation method involves a two-step process, where Cu15Si4 nanowires are synthesized from a Cu substrate via a solvent vapor growth (SVG) approach followed by the plasma-enhanced chemical vapor deposition (PECVD) of aSi. These binder-free anodes are investigated in half-cell (versus Li-foil) and full-cell (versus LCO) configurations with discharge capacities greater than 2000 mAh/g retained after 200 cycles (half-cell) and reversible capacities of 1870 mAh/g exhibited after 100 cycles (full-cell). A noteworthy rate capability is also attained where capacities of up to 1367 mAh/g and 1520 mAh/g are exhibited at 5C in half-cell and full-cell configurations, respectively, highlighting the active material's promise for fast charging and high power applications. The anode material is characterized prior to cycling and after 1, 25, and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material.

Three-dimensional micromachined diamond birdbath shell resonator on silicon substrate

This paper proposes a novel three-dimensional (3-D) micromachined birdbath shell resonator ($$\mathrm {\upmu }$$-BSR) fabricated from polycrystalline diamond on silicon substrate for potential MEMS gyroscope. Design, modal simulation, MEMS fabrication process and vibration test of the micromachined diamond birdbath shell resonator are presented. Key features of the 3-D fabrication process are the etching of the bulk silicon mold and deposition of high-Q polycrystalline diamond films onto the mold. The birdbath shell resonator is fabricated with a good structural symmetry, owing to its supporting anchor and shell are integrated manufactured through the MEMS fabrication process. By using piezoelectric actuation and optical characterization, the M = 2 elliptical vibration mode is determined to be at about 80.61 kHz with a normalized frequency split ($$\varDelta {f_{M = 2}}/{f_{M = 2}}$$) of 0.32%. The frequency separation between the M = 2 elliptical mode and the closest parasitic tilting mode of the $$\upmu $$-BSR is relatively large, which makes the resonator less sensitive to vibration and improves shock resistance. These resonators show great promise for being used as micro birdbath resonator gyroscopes ($$\upmu $$-BRGs) on a chip.

Olive Nutritional Status and Tolerance to Biotic and Abiotic Stresses.

The role of nutrients in plant growth is generally explained in terms of their functions in plant metabolism. Nevertheless, there is evidence that plant tolerance or resistance to biotic or abiotic stresses could be affected by the nutritional status. Although not well studied, an adequate nutritional status for optimal plant growth is thought to also be optimal for plant tolerance to stress. Considering the current global trend toward sustainability, studies that clarify the relationships between nutrition and stress are of great interest. For example, potassium plays an important role in the regulation of water status in the olive, improving drought tolerance, while calcium is involved in sodium exclusion mechanism, which can increase tolerance to salinity. Nitrogen excess, in contrast, increases susceptibility to spring frost and olive leaf spot. Silicon is not an essential element for plant growth, but it is considered a beneficial element; among its roles in the control of pests and diseases is the formation of a physical barrier that occurs through silicon deposition in the epidermal cells of the leaves. The presence of soluble silicon also facilitates the deposition of phenolic and other compounds at sites of infection, which is a general defense mechanism to pathogen attack. In olive, silicon application, either by foliar sprays or through irrigation water, reduces the incidence of olive leaf spot. This review summarizes the current status of olive nutrition, the relationships with biotic and abiotic stresses, and the effects of silicon.

Electrophoretic deposition of bi-layered nano-sized silicon carbide/mullite coating from stabilized suspensions

Nano-sized silicon carbide/mullite bi-layered film was applied onto the surface of graphite using electrophoretic deposition (EPD) method from stabilized suspensions. The suspensions were prepared adding 5 g L−1 SiC and 10 g L−1 mullite in ethanol. The effects of adding various amounts of polyethylene imine (PEI) on the stability of suspensions were investigated by visual inspection (sedimentation height), measuring the zeta potential, and particle size distribution. As a result, the addition of 6.0 dwb% and 1.5 dwb% PEI to SiC and mullite suspensions were found to be an effective way in dispersing of nanoparticles. The zeta potential values of well-stabilized suspensions were determined 37.6 mV and 42.4 mV for SiC and mullite suspensions, respectively. Therefore, the coating processes were conducted with the optimal amounts of PEI. In the deposition process, the optimal distance between electrodes was determined 10 mm. In order to investigate the coating process parameters, the optical microscopy (OM) was used for single-layer coatings. The results reveal that applied voltages of 40 V and 10 V with deposition periods of 50 s and 60 s bring about uniform coatings. In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were carried out to evaluate the microstructure. The thicknesses of green coatings were measured about 24.15 μm for SiC layer and 7.23 μm for the mullite layer.

Photo cured 3D porous silica-carbon (SiO2–C) membrane as anode material for high performance rechargeable Li-ion batteries

Silicon based anode materials has got significant attention in recent years due to its environmental affinity, lower cost and high capacity in lithium ion batteries. The Photo cured 3D porous Silica-carbon membrane (SiO2–C material) was synthesized via binary phase solid state photo-polymerization, freeze dried to obtain porous membrane and then used as template to get silica deposited membrane by chemical vapor deposition method (CVD) at 30 °C, followed by calcination. The silicon deposition has been confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS). The Barret-Joyner-Halenda (BJH) pore size distribution results showed the pore size of 10.2924 nm and surface area of 21.1957 m2/g with cumulative pore volume of 0.040248 cm³/g. The first discharge capacity reached to 719 mAhg−1 with 79.94% columbic efficiency regarding first cycle and discharge capacity for 100 cycles reached to 693 mAhg−1 with 99% columbic efficiency, which indicated high reaction reversibility. The silicon deposition with a porous structure improved the electronic conductivity and stabilized the material. The better electrochemical performance observed could be due to porous structure and carbon matrix of SiO2–C material.

Influence of the Substrate on the Electrodeposition of Silicon from Ionic Liquids

Silicon is an important semiconductor, used in many electronic components. In addition, it also finds application in conversion of solar energy and electrochemical energy storage. The high theoretical capacity of more than 4 Ah/g makes Si an attractive alloying material for anodes in Lithium-Ion Batteries (LIB) [1]. However, one major drawback of the Si-based materials is the complicated and expensive fabrication process. Among the other methods, electrodeposition is a low-cost and simple alternative because it allows adjusting the properties of the silicon layer by varying the electrochemical parameters. Elemental silicon is highly reactive, for which reason the deposit can react with the substrate and/or the electrolyte. The aim of this work is to investigate the substrate influence on the electrochemistry of the silicon deposition from an Ionic Liquid (IL) and to analyze its impact on the composition of the resulting layers. As highly stable and low volatile solvents, ionic liquids offer the opportunity for an effective silicon electrodeposition. Cu and Ni were selected as substrates with the perspective to further apply them as porous hosts for Si in LIBs. For comparison, vitreous carbon (GC) was used as an inert material. The electrolyte consisted of 0.5 M SiCl4 dissolved in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSI]. The electrochemical reduction of SiCl4 was studied with linear sweep voltammetry (LSV). Chronoamperometry, coupled with electrochemical quartz crystal microbalance (QCM) was used to investigate the mass-charge balance of the deposition process. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied for the analysis of the surface and the composition of the obtained layers. The voltammetric data exhibited just one peak for vitreous carbon, indicating a one-step reduction of SiCl4 (fig. 1). In contrast, three peaks for Cu and two peaks and two shoulders for nickel were observed. Simultaneously performed QCM measurements did not show any frequency change above -1.3 V in the case of nickel, which indicates that the first reduction processes (E > -1.3V) are not correlated with any bulk deposition, but could be related to a partial reduction of the precursor to soluble species SixCl4-y. A similar behavior can be observed for the copper substrate. Until -1.0 V the frequency of the quartz crystal did not change and the following decrease is so small, that bulk deposition can be ruled out. The partial reduction of SiCl4 to a soluble species SixCly and/or adsorption phenomena on the electrode surface can be an explanation for this observation. At more cathodic potentials (E < -1.3 V) the resonance frequency of the QCM decreases, which corresponds to a mass increase at the electrode surface. The evaluation of the potentiostatic EQCM data results in MQCM/Cu = 65.2 g/mol and MQCM/Ni = 52.5 g/mol, assuming a transfer of four electrons. This is quite different compared to the theoretical value of Mtheo = 28.1 g/mol and can be related to an entrapment of the electrolyte or its decomposition products. However, after 60 minutes the frequency change reached a steady state for both substrates accompanied with a strong damping increase. The deposition is inhibited at this point, which is probably due to the low conductivity of the deposited layer. The XPS measurements confirm the assumption about the entrapment of IL into the deposits. Furthermore, the data exhibit a high reactivity of silicon resulting in the formation of metal silicides at the interface for Cu and Ni. This supposition is underpinned by the absence of the signal for Si0 for samples, which were stored under argon for several weeks before the XPS measurements (fig. 1). Nevertheless, this can enhance the adhesion of the deposit. The performances of these silicon layers in LIBs were investigated by galvanostatic cycling in EC/DMC (1:1) with 10% FEC and 1 M LiPF6. [1] Vlaic, Codruta Aurelia, et al. "Electrochemical lithiation of thin silicon based layers potentiostatically deposited from ionic liquid." Electrochimica Acta 168 (2015): 403-413. Figure 1

Silicon variation and phytolith morphology in different organs of Dendrocalamus brandisii (Munro) Kurz (Bambusoideae)

Silicon is an essential element for the growth and development of bamboo plants that significantly affects the biochemical and physical properties for industrialized bamboo utilization. Silicon is biomineralized as diverse forms of phytoliths in the bamboo organs. We investigated the silicon variation and phytolith morphology in different organs of Dendrocalamus brandisii (Munro) Kurz. The silicon content in D. brandisii (Munro) Kurz varies and increases in the order of leaf > sheath > branch > culm > shoot > root. The phytolith morphotypes and presence frequency in different D. brandisii organs varied closely interrelated with the cell structure and organ functions. Amorphous silicon deposition and few varieties and numbers of phytolith were found in D. brandisii root and shoots. Rich distribution of the saddle and dumb-bell phytoliths was found in all organs except the root and mature culm and branch. More elongate and rectangular phytoliths were found in mature culm and branch. Round and elliptical phytoliths might be firstly formed followed by dumb-bell and saddle phytoliths. Phytolith sizes increased with increasing culm, branch and leaf age, but did not demonstrate a specific trend with culm height. The result could contribute to enriching phytolith morphology in Gramineae and provide theoretical basis and references for plant taxonomy and large-scale bamboo industrial processing and utilization.

Toxidez de manganês na planta de arroz atenuada pela ação do silício nos tecidos foliares

Anatomical modifications of leaves and other organs associated with mineral nutrition have been observed in many plants. However, little is known about the quantitative effects of Si and Mn on the anatomy of plant leaves, especially in rice. This study aimed to quantify the tissue thickness of rice leaves and the density of silica bodies in rice leaves grown in a nutrient solution supplemented with Si and Mn and evaluate the possible effects of Si on Mn toxicity. Treatments were arranged in a 2×3 factorial scheme = six combinations of treatments, two doses of Si (0 and 2 mmol L-1), and three doses of Mn (0.5, 2.5, and 10 µmol L-1) in randomized complete block design with four replications. After 39 days in the nutrient solution with the respective treatments, anatomical and micromorphometric measures of the leaf blade were carried out to determine the thickness and area of leaf tissues. The data were submitted to analysis of variance (ANOVA) and Tukey’s multiple comparisons test of means(p?0,05). The abaxial and adaxial epidermal thickness, as well as the density of silica bodies increased with the addition of Si to the nutrient solution. This study demonstrated that Si reduced the number of vascular bundles and Mn reduced the thickness of the chlorenchyma with increasing doses. Manganese doses of up to 10 ?mol L-1 do not inhibit the uptake and deposition of silicon in rice leaf tissues. Higher Si concentration in the solution caused anatomical changes in the leaf, which was associated with a possible alleviation of Mn toxicity due to the higher concentration of Si in plants since this effect was observed mainly when Si was present in the nutrient solution.

Phytolith Formation in Plants: From Soil to Cell.

Silica is deposited extra- and intracellularly in plants in solid form, as phytoliths. Phytoliths have emerged as accepted taxonomic tools and proxies for reconstructing ancient flora, agricultural economies, environment, and climate. The discovery of silicon transporter genes has aided in the understanding of the mechanism of silicon transport and deposition within the plant body and reconstructing plant phylogeny that is based on the ability of plants to accumulate silica. However, a precise understanding of the process of silica deposition and the formation of phytoliths is still an enigma and the information regarding the proteins that are involved in plant biosilicification is still scarce. With the observation of various shapes and morphologies of phytoliths, it is essential to understand which factors control this mechanism. During the last two decades, significant research has been done in this regard and silicon research has expanded as an Earth-life science superdiscipline. We review and integrate the recent knowledge and concepts on the uptake and transport of silica and its deposition as phytoliths in plants. We also discuss how different factors define the shape, size, and chemistry of the phytoliths and how biosilicification evolved in plants. The role of channel-type and efflux silicon transporters, proline-rich proteins, and siliplant1 protein in transport and deposition of silica is presented. The role of phytoliths against biotic and abiotic stress, as mechanical barriers, and their use as taxonomic tools and proxies, is highlighted.

Surface Erosion of Plasma-Facing Materials Using an Electrothermal Plasma Source and Ion Beam Micro-Trenches

Erosion characteristics of tungsten-alternative plasma-facing materials (PFMs) were tested under high heat flux conditions in the electrothermal plasma source facility at Oak Ridge National Laboratory. The PFMs of interest are high-purity β-3C chemical vapor deposition silicon carbide (SiC) and the MAX phases Ti3SiC2 and Ti2AlC [MAX = chemical formula Mn+1AXn, where M is an early transition metal (such as Ti or Ta), A is an A-group element (such as Si or Al), and X is carbon or nitrogen]. An erosion analysis method was developed using a combination of focused ion beam microscopy and scanning electron microscopy, carving micro-trench geometries into polished sample surfaces. Samples of SiC, Ti3SiC2, and Ti2AlC were exposed to the electrothermal plasma source alongside tungsten and monocrystalline silicon. Samples were exposed to a Lexan polycarbonate (C16H14O3) electrothermal plasma stream in a He environment, at a specified impact angle, with infrared camera diagnostics. Edge localized mode–relevant heat fluxes of 0.9 to 1 GW/m2 over 1-ms discharges were generated on the target surfaces. Tungsten samples exhibited pronounced melt-layer formation and deformation, with measured molten pits 2 to 10 μm in diameter and melt-layer depths of up to 7 μm deep. Surface erosion rates for Ti3SiC2 and Ti2AlC ranged from 80 to 775 μm/s and 85 to 470 μm/s, respectively. Both MAX phases exhibited extreme surface fracture and material ejection, with damage depths past 4 μm for Ti2AlC and 11 μm for Ti3SiC2. SiC displayed the best performance, in one case surviving 15 consecutive electrothermal plasma exposures with an average erosion rate of about 29 μm/s and no surface fracturing. SiC erosion rates ranged from 23 to 128 μm/s.

Highly sensitive CMUT-based humidity sensors built with nitride-to-oxide wafer bonding technology

In this paper, we present highly sensitive capacitive micromachined ultrasonic transducer (CMUT) based gravimetric humidity sensors that are fabricated with nitride-to-oxide wafer bonding technology. In contrast to conventional wafer bonding CMUT processes that use expensive silicon-on-insulator (SOI) wafers to produce resonating membranes, the proposed process employs low-pressure chemical vapor deposition (LPCVD) silicon nitride as the membrane material. The proposed process provides thinner and lighter membranes, and thus more sensitive CMUT resonators. Furthermore, additional benefits such as reduced fabrication complexity and more controllable membrane thickness are possible. Ten MHz CMUTs were designed, fabricated and functionalized by graphene oxide (GO) with three different concentrations. The device uniformities and resonance frequencies were characterized by a laser vibrometer and a vector network analyzer. Humidity sensing performance of the sensors was analyzed through the resonance shifts in a relative humidity (RH) range of 11.3%–93.6%. The CMUT coated with the highest concentration of GO (0.5 mg/ml) exhibited the highest sensitivity of up to 15.3 kHz/%RH. Decent repeatability and a short response/recovery time were achieved by all the CMUT sensors. This study demonstrates that the CMUT humidity sensors that are realized with nitride-to-oxide bonding technology can be an excellent candidate for humidity sensing due to their high sensitivity and CMOS-compatible fabrication process.

Electrodeposition of Silicon with a Liquid Gallium Cathode in Molten Salts

Further development of solar power depends largely on the availability of inexpensive solar grade silicon. Electrodeposition is a candidate method to produce high purity silicon at a reasonable cost. We have previously studied electrodeposition of silicon from molten calcium chloride based electrolytes and molten fluoride electrolytes. Recent experiments were carried out by using a liquid gallium cathode. The approach is based on studies by Stephen Maldonado and coworkers [1] of electrodeposition of silicon by using a liquid gallium cathode in an organic based electrolyte. Silicon has a low tendency to alloy with gallium. Electrochemical studies and electrolysis to deposit silicon from molten eutectic KCl – KF with 2 mol% K2SiF6 were carried out at 650 oC. Silver wire and glassy carbon rod were used as working electrodes, while glassy carbon rod or silver wire were counter electrodes. A silicon flag reference electrode was used. Liquid gallium in a small alumina tube with tungsten lead was the cathode during electrolysis while glassy carbon or silicon was the anode. Silicon deposition is diffusion controlled on silver cathode, while silicon deposition is charge transfer controlled on liquid gallium cathode. Silicon was found to deposit using a liquid gallium cathode, both during galvanostatic and potentiostatic electrolysis. The current efficiency was found to be quite high, and consistently above 80 %. Some silicon particles were found on top of gallium after cooling down. A much larger amount of gallium was used in recent experiments. This helped to form silicon particles inside the liquid gallium cathode. Silicon was recovered after experiments by physical separation from liquid gallium followed by dissolution of gallium in concentrated HNO3. High purity silicon was obtained. Gallium can form alloys with many impurity elements which may cause a refining effect of silicon. The use of a liquid gallium cathode is promising for the prospect of developing a new process for producing high purity silicon by electrolysis in molten salts.

Microfluidic Chemotaxis Assay through Stable Chemical Gradient

The diffusion-based method can create a non-flow environment for the bacteria, so chemotaxis response can be observed in gradients that evolve only by diffusion, in the absence of flow. Recently, we have reported a convenient and reliable diffusion-based microfluidic device for nonlinear gradient generation. Stable and rapid diffusion of chemicals was successfully generated by direct contact of two fluids manipulated by control of capillary action. In our design, the height of the junction channel is very critical because the junction channel play key roles in diffusion-based gradient generation and physical prevention of bacterial movement toward the chemoeffector channel in analysis of positive chemotactic response. In this study, to improve the height accuracy of the junction channel, we propose a new alternative microfabrication method using thick silicon oxide deposition and reactive ion etching. The height of the junction channel within 1% accuracy could be precisely fabricated by the newly-proposed microfabrication. As a proof-of-concept, we conducted experiments with bacterial chemoeffectors with Pseudomonas aeruginosa PAO1 based on fluorescent observation in a concentration-dependent manner. We easily achieved chemotaxis index of each chemoeffector and it was in a good agreement with our previous result while the variation of chemotaxis index is reduced to be half. We envision that our proposed fabrication will guide microfluidic fabrication to techniques for reproducibility for various field.

Flash Lamp Annealed Polycrystalline Silicon TFT Dependence on Surface Morphology and the Back-Channel Material Interface

This work studies the operation of polycrystalline silicon p-channel TFTs prepared via Flash Lamp Annealing (FLA). Silicon nitride was investigated as a back-channel interface layer to suppress void formation via dewetting of molten silicon. Predefined polygons of amorphous silicon were crystallized on display glass using single-pulse FLA exposure. Two distinct surface morphologies were realized within the same exposed region as a result of the underlying silicon nitride film and localized variation in the substrate thermal contact during PECVD deposition of amorphous silicon. While both resulting morphologies have polysilicon grains on micron scale, differences in TFT electrical behavior appear to coincide with differences in grain structure and boundary regions. The electrical results also indicate inferior electrical performance in response to the back-channel silicon nitride in comparison to results demonstrated on SiO2. Extracted parameters provide a quantitative assessment of the device operation as related to surface morphology and the back-channel material interface.

Electrochemical deposition of silicon from a sulfolane-based electrolyte: Effect of applied potential

As a low-cost, non-volatile, highly polar and chemically stable solvent, sulfolane has a high implementation potential for electroplating in organic media. This is the first report of the electrodeposition of silicon from sulfolane-based electrolytes. Voltammetric and chronoamperometric techniques, coupled with a quartz crystal microbalance, have been used to perform and characterize the process. Resonance frequency, f, damping, w, and apparent molar mass, Mapp are used as sensitive parameters for the evaluation of the silicon layer formation. Si electrodeposition displays a strong dependence on the applied potential. Close to theoretical values for Mapp and minimal w are observed at low deposition overpotentials, which allow an in situ quantitative mass evaluation. At higher overpotentials the process efficiency decreases due to simultaneous electrolyte decomposition. The electrodeposition of elemental Si (approx. 60% of the entire Si content) is evidenced by X-ray photoelectron spectroscopy. Additionally, the formation of a binary metal compound with the Cu substrate might be a key factor in the very good adhesion and mechanical stability of the layer.

Electrodeposition of Silicon with a Liquid Gallium Cathode in Molten Salts

Further development of solar power depends largely on the availability of inexpensive solar grade silicon. Electrodeposition is a candidate method to produce high purity silicon at a reasonable cost. A new approach using a liquid gallium cathode was used to study deposition of silicon from molten salt electrolytes containing K2SiF6. Electrochemical studies and electrolysis to deposit silicon from molten eutectic KCl–KF with additions of K2SiF6 were carried out at 650 oC. Silver wire and glassy carbon rod were used as working electrodes, while glassy carbon rod or silver wire were counter electrodes. A silicon plate reference electrode was used. Liquid gallium in a small alumina tube with tungsten lead was the cathode during electrolysis while glassy carbon or silicon was the anode. Silicon was found to deposit inside a liquid gallium cathode during electrolysis. The current efficiency was found to be quite high, and consistently above 80 %.

Pyramid size control and morphology treatment for high-efficiency silicon heterojunction solar cells

This paper investigates the formation process of surface pyramid and etching characteristics during the texturing process of mono-crystalline silicon wafers. It is found that there is an etch rate transition point in alkaline anisotropic etching when {100} plane-dominated etch turns to {111} plane-dominated etch, and the pyramid size has a strong linear correlation with the etch amount at the transition point. Several techniques were developed to control the pyramid size by monitoring and adjusting the etching amount. A wide range of average pyramid sizes were successfully achieved, from 0.5 to 12 μm. The experiments of the pyramid size on the light reflectance, the minority carrier lifetime (MCLT), and the performance of silicon heterojunction (SHJ) solar cells were carried out and analyzed. A desirable range of pyramid sizes was empirically determined by our investigation. In order to reduce the density states on the texturing surface, the wet-chemical smoothing treatment was also investigated. The smoothing treatment improves the passivation quality and the performance of the solar cells. Through pyramid size control and morphology treatment, together with the amorphous silicon (a-Si:H) deposition improvement, and electrode optimization, high performance of SHJ solar cells has been achieved, up to conversion efficiency 23.6%.

Hot wire chemical vapor deposition for silicon photonics: An emerging industrial application opportunity

In this work different silicon photonic devices, including straight waveguides, multi-mode interference devices and Mach-Zehnder interferometers, were fabricated and characterized on hot-wire chemical vapor deposition (HWCVD) silicon nitride (SiN) layers deposited at temperatures below 350 °C. These layers presented a hydrogen concentration of 13.1%, which is lower than that achieved with plasma enhanced chemical vapor deposition at these deposition temperatures. The lowest reported optical propagation losses of 6.1 dB/cm and 5.7 dB/cm, 1550 nm and 1310 respectively, for straight SiN waveguides prepared by HWCVD was measured. We demonstrated that silicon nitride SiN, prepared using HWCVD, is a viable material for silicon photonics fabrication.

Synthesis and Exploratory Deposition Studies of Isotetrasilane and Reactive Intermediates for Epitaxial Silicon.

A synthetic method is presented for the production of isotetrasilane, a higher order perhydridosilane, with the purity and volume necessary for use in extensive studies of the chemical vapor deposition (CVD) of epitaxial silicon (e-Si) thin films. The chemical characteristics, thermodynamic properties, and epitaxial film growth of isotetrasilane are compared with those of other perhydridosilanes. A film-growth mechanism distinct from linear perhydridosilanes H(SiH2) nH, where n ≤ 4, is reported. Preliminary findings are summarized for CVD of both unstrained e-Si and strained e-Si doped with germanium (Ge) and carbon (C) employing isotetrasilane as the source precursor at temperatures of 500-550 °C. The results suggest that bis(trihydridosilyl)silylene is the likely deposition intermediate under processing conditions in which gas-phase depletion reactions are not observed.

Silicon Deposition in Leaf Trichomes of Cucurbitaceae Horticultural Plants: A Short Report

Silicon deposition in leaf trichome of six horticultural Cucurbitaceae species, cucumber (Cucumis sativus), pumpkin (Cucurbita maxima), melon (Cucumis melo), watermelon (Citrullus lanatus), sponge gourd (Luffa cylindrica) and bottle gourd (Lagenaria siceraria var. hispida) was observed by an X-ray microanalyzer coupled with an environmental scanning electron microscope. The elements that presented in the surface of three or four leaves of the individual species were detected and mapped by the X-ray microanalyzer. In leaves of cucumber, pumpkin, and melon, high accumulation of silicon was detected in cells surrounding the bases of the trichome hair and the hair itself deposited calcium. On the other hand, in sponge gourd and bottle gourd, high accumulation of silicon was detected only in the hair. In watermelon leaves, silicon deposited both in the hair and in cells surrounding the bases of the hair. Thus, horticultural Cucurbitaceae plants have interspecific variation in the pattern of silicon deposition in leaf trichomes.