Saturday, October 26, 2013

Monocrystalline silicon is expensive to produce

Monocrystalline silicon is expensive to produce, and is usually only justified in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. IBM ThinkPad T61 8898 CPU Fan For other uses, other types of pure silicon which do not exist as single crystals may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) which are used in the production of low-cost, large-area electronics in applications such asliquid crystal displays, and of large-area, low-cost, thin-film solar cells. IBM ThinkPad R50p 2889 CPU Fan Such semiconductor grades of silicon which are either slightly less pure than those used in integrated circuits, or which are produced in polycrystalline rather than monocrystalline form, make up roughly similar amount of silicon as are produced for the monocrystalline silicon semiconductor industry, or 75,000 to 150,000 metric tons per year. IBM ThinkPad R50p 1830 CPU Fan However, production of such materials is growing more quickly than silicon for the integrated circuit market. By 2013 polycrystalline silicon production, used mostly in solar cells, is projected to reach 200,000 metric tons per year, while monocrystalline semiconductor silicon production (used in computer microchips) remains below 50,000 tons/year. IBM ThinkPad R50 1829 CPU Fan Although silicon is readily available in the form of silicates, very few organisms have a use for it. Diatoms, radiolaria andsiliceous sponges use biogenic silica as a structural material to construct skeletons. In more advanced plants, the silicaphytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, for example rice, need silicon for their growth.[58][59][60] IBM ThinkPad R50P CPU Fan Although silicon was proposed to be an ultra trace nutrient, its exact function in the biology of animals is still under discussion. Higher organisms are only known to use it in very limited occasions in the form ofsilicic acid and soluble silicates.[citation needed] Silicon is known to be needed for synthesis of elastin and collagen; the aorta contains the highest quantity of elastin and silicon.[61] IBM Thinkpad W500 CPU Fan Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)."[62][63] Silicon has been shown in university and field studies to improve plant cell wall strength and structural integrity,[64] improve drought and frost resistance, decrease lodging potential and boost the plant's natural pest and disease fighting systems.[65] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[64] Compaq Presario CQ41-206TU CPU Fan Hypothetical silicon-based lifeforms are the subject of silicon biochemistry, by analogy with carbon-based lifeforms. Silicon, being below carbon in the periodic table, is thought to have similar enough properties that would make silicon-based life possible, but much different from life as we know it. Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates. It offers some unique capabilities for a variety of electronics.  SONY Vaio VPC-EB4X1E/BQ CPU Fan Silicon is a fourfold coordinated atom that is normally tetrahedrally bonded to four neighboring silicon atoms. In crystalline silicon (c-Si) this tetrahedral structure continues over a large range, thus forming a well-ordered crystal lattice. In amorphous silicon this long range order is not present. Rather, the atoms form a continuous random network. HP G62-374CA CPU Fan Moreover, not all the atoms within amorphous silicon are fourfold coordinated. Due to the disordered nature of the material some atoms have a dangling bond. Physically, these dangling bonds represent defects in the continuous random network and may cause anomalous electrical behavior. Likewise, the material can be passivated by hydrogen, which bonds to the dangling bonds and can reduce the dangling bond density by several orders of magnitude. HP Pavilion dv5-1203eg CPU Fan Hydrogenated amorphous silicon (a-Si:H) has a sufficiently low amount of defects to be used within devices such as solar photovoltaic cells, particularly in theprotocrystalline growth regime.[1][2] However, hydrogenation is unfortunately associated with light-induced degradation of the material, termed the Staebler–Wronski effect. HP Pavilion dv7-3131ez CPU Fan Amorphous alloys of silicon and carbon (amorphous silicon carbide, also hydrogenated, a-Si1-xCx:H) are an interesting variant. Introduction of carbon atoms adds extra degrees of freedom for control of the properties of the material. The film could also be made transparent to visible light. Increasing concentrations of carbon in the alloy widen the electronic gap between conduction and valence bands (also called "optical gap" and bandgap). Dell Vostro 3450 CPU Fan This can potentially increase the light efficiency of solar cells made with amorphous silicon carbide layers. On the other hand, the electronic properties as asemiconductor (mainly electron mobility), are adversely affected by the increasing content of carbon in the alloy, due to the increased disorder in the atomic network. Several studies are found in the scientific literature, mainly investigating the effects of deposition parameters on electronic quality, SONY Vaio VGN-CR23/N CPU Fan but practical applications of amorphous silicon carbide in commercial devices are still lacking. While a-Si suffers from lower electronic performance compared to c-Si, it is much more flexible in its applications. For example, a-Si layers can be made thinner than c-Si, which may produce savings on silicon material cost. One further advantage is that a-Si can be deposited at very low temperatures, e.g., as low as 75 degrees Celsius. HP Pavilion dv6-3043tx CPU Fan This allows for deposition on not only glass, but plastic as well, making it a candidate for a roll-to-roll processing technique. Once deposited, a-Si can be doped in a fashion similar to c-Si, to form p-type or n-type layers and ultimately to form electronic devices. Another advantage is that a-Si can be deposited over large areas by PECVD. HP Pavilion dv6-3163eo CPU Fan The design of the PECVD system has great impact on the production cost of such panel, therefore most equipment suppliers put their focus on the design of PECVD for higher throughput, that leads to lower manufacturing cost[4] particularly when thesilane is recycled.[5] Amorphous silicon has become the material of choice for the active layer in thin-film transistors (TFTs), which are most widely used in large-area electronicsapplications, mainly for liquid-crystal displays (LCDs). HP Pavilion dv7-1003eo CPU Fan a-Si has been used as a photovoltaic solar cell material for devices which require very little power, such as pocket calculators, because their lower performance compared to traditional c-Si solar cells is more than offset by their simplified and lower cost of deposition onto a substrate. More recently, improvements in a-Si construction techniques have made them more attractive for large-area solar cell use as well. Dell Vostro 3450 CPU Fan Here their lower inherent efficiency is made up, at least partially, by their thinness – higher efficiencies can be reached by stacking several thin-film cells on top of each other, each one tuned to work well at a specific frequency of light. This approach is not applicable to c-Si cells, which are thick as a result of their construction technique and are therefore largely opaque, blocking light from reaching other layers in a stack.  HP Pavilion dv7-3067nr CPU Fan The main advantage of a-Si in large scale production is not efficiency, but cost. a-Si cells use approximately 1% of the silicon needed for typical c-Si cells, and the cost of the silicon is by far the largest factor in cell cost (no source). However, the higher costs of manufacture due to the multi-layer construction have, to date, made a-Si unattractive except in roles where their thinness or flexibility are an advantage. SONY Vaio VGN-CR23/N CPU Fan Typically, amorphous silicon thin-film cells use a p-i-n structure. Typical panel structure includes front side glass, TCO, thin film silicon, back contact,polyvinyl butyral (PVB) and back side glass. UNI-SOLAR, a division of Energy Conversion Devices produces a version of flexible backings, used in roll-on roofing products. Photovoltaic thermal hybrid solar collectors(PVT), are systems that convert solar radiation into thermal and electrical energy. HP Pavilion dv7-1129wm CPU Fan These systems combine aphotovoltaic cell, which converts electromagnetic radiation (photons) into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the PV module. Photovoltaic (PV) cells suffer from a drop in efficiency with the rise in temperature due to increased resistance. HP Pavilion G72-b15EV CPU Fan Most such systems can be engineered to carry heat away from the PV cells thereby cooling the cells and thus improving their efficiency by lowering resistance.[6]Although this is an effective method, it causes the thermal component to under-perform compared to a solar thermal collector. Recent research showed that a-Si:H PV with low temperature coefficients allow the PVT to be operated at high temperatures, creating a more symbiotic PVT system and improving performance of the a-Si:H PV by about 10%.Compaq Presario CQ60-417DX CPU Fan Microcrystalline silicon (also called nanocrystalline silicon) is amorphous silicon, but also contains small crystals. It absorbs a broader spectrum of light and is flexible. Micromorphous silicon module technology combines two different types of silicon, amorphous and microcrystalline silicon, in a top and a bottom photovoltaic cell. HP Pavilion dv7-3080eg CPU Fan Sharp produces cells using this system in order to more efficiently capture blue light, increasing the efficiency of the cells during the time where there is no direct sunlight falling on them. Protocrystalline silicon is often used to optimize the open circuit voltage of a-Si photovoltaics. Xunlight Corporation, which has received over $40 million of institutional investments,[ HP Pavilion dv9233ca CPU Fan has completed the installation of its first 25 MW wide-web, roll-to-roll photovoltaic manufacturing equipment for the production of thin-film silicon PV modules.[9] Anwell Technologies has also completed the installation of its first 40 MW a-Si thin film solar panel manufacturing facility in Henan with its in-house designed multi-substrate-multi-chamber PECVD equipment. HP Envy 14-1195la CPU Fan Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells. In single crystal silicon, the crystalline framework is homogenous, which can be recognized by an even external colouring.[1HP Pavilion dv6-2115sf CPU Fan ]In single crystal silicon, also called monocrystal, the crystal lattice of the entire sample is continuous and unbroken with no grain boundaries. Large single crystals are exceedingly rare in nature and can also be difficult to produce in the laboratory (see also recrystallisation). In contrast, in an amorphous structure the order in atomic positions is limited to short range. HP Pavilion dv7-3067nr CPU Fan Polycrystalline and paracrystalline phases (see Polycrystal) are composed of a number of smaller crystals or crystallites.Polycrystalline silicon (or semicrystalline silicon, polysilicon, poly-Si, or simply "poly") is a material consisting of multiple small silicon crystals. Polycrystalline cells can be recognized by a visible grain, a “metal flake effect”. HP Pavilion dv7-1129wm CPU Fan Semiconductor grade (also solar grade) polycrystalline silicon is converted to "single crystal" silicon – meaning that the randomly associated crystallites of silicon in "polycrystalline silicon" are converted to a large "single" crystal. Single crystal silicon is used to manufacture most Si-based microelectronic devices. Polycrystalline silicon can be as much as 99.9999% pure.[2] HP Pavilion G72-b15EV CPU Fan Ultra-pure poly is used in the semiconductor industry, starting from poly rods that are two to three meters in length. In microelectronic industry (semiconductor industry), poly is used both at the macro-scale and micro-scale (component) level. Single crystals are grown using the Czochralski process, float-zone and Bridgman techniques. HP Pavilion dv6-2140se CPU Fan At the component level, polysilicon has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it is deposited using low-pressure chemical-vapour deposition (LPCVD) reactors at high temperatures and is usually heavily doped n-type or p-type. SONY Vaio VGN-SZ6RXN/C CPU Fan

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