Plasma-enhanced chemical vapor deposition advantage

The Si thin-film solar cells on glass, available on the market today, are mainly based on hydrogenated amorphous Si(a-Si H) and hydrogenated microcrystalline Si(pc-Si H). Both are usually prepared by plasma enhanced chemical vapor deposition (PECVD). A big advantage of both technologies is that the Si films can be prepared at very low temperatures (below 300°C). Although stabilized single-junction solar cell efficiencies of about 10% have... 

While amorphous silicon TFT sulfers from low electronic performance, it is very flexible in application and manufacturing. One important advantage is that amorphous Si can be deposited at temperatures as low as 75°C. This makes it possible for the device to be made not only on glass, but also on plastics. In addition, amorphous silicon can be deposited over very large areas by plasma-enhanced chemical vapor deposition (PECVD) with standard industrial equipments. Both features make mass-scale production of amorphous silicon TFT-based devices relatively easy and economic. The main application for amorphous silicon TFT is on liquid crystal displa (LCDs), in which each pixel is individually driven by a TFT transistor. 

CVD is a well-understood thin film deposition method that uses chemical reactions of vapor-phase precursors. CVD processes have traditionally been initiated and controlled by heat as the source of energy. An elevated deposition temperature is normally required, which restricts the types of substrates that can be used and coating materials that can be deposited, especially thermally sensitive ones (Jones and Hitchman, 2009). However, thermal energy is not the only energy supplied to the system plasmas and photons are widely used in CVD processes. Plasma-enhanced chemical vapor deposition (PECVD), or plasma-assisted CVD, is a CVD technique in which plasma in lieu of thermal energy is used primarily to activate ions and radicals in the chemical reactions leading to layer formation on the substrate. One major advantage of PECVD over... 

Chemical vapor deposition includes various systems, and they are low-pressure CVD (LPCVD), atmospheric pressure CVD (APCVD), plasma enhanced CVD (PECVD), and others. Each type of CVD system has its own advantages and limitations. For instance, in LPCVD, the reactor is usually operated at 1 torr. Under this condition, the diffusivity of the gaseous species increases significantly compared to that under atmospheric pressure. Consequently, this increase in transport of the gaseous species to the reaction sites and the by-products from the reaction sites in LPCVD will not become the rate-limiting steps. This leads to the surface reaction step to be the rate limiting one. 

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