Nanocrystalline silicon 197129 203249840 2008-04-04T09:10:58Z 140.78.119.20 {{Unreferenced|date=February 2008}} [[Image:Nano_Si_640x480.jpg|thumb|300px|right|Silicon nanopowder]] '''Nanocrystalline silicon''' ('''nc-Si''')—an [[allotropy|allotropic]] form of [[silicon]] with [[paracrystalline]] structure—is similar to [[amorphous silicon]] (a-Si), in that it has an [[amorphous solid|amorphous]] phase. Where they differ, however, is that nc-Si has small grains of crystalline silicon within the amorphous phase. This is in contrast to [[polycrystalline silicon]] (poly-Si) which consists solely of crystalline silicon grains, separated by grain boundaries. nc-Si is sometimes also known as '''microcrystalline silicon''' (μc-Si). The difference comes solely from the grain size of the crystalline grains. Most materials with grains in the micrometre range are actually fine-grained polysilicon, so nanocrystalline silicon is a better term. The term Nanocrystalline silicon refers to a range of materials around the transition region from amorphous to microcrystalline phase in the silicon thin film. The crystalline volume fraction (as measured from [[Raman spectroscopy]]) is another criteriòn to describe the materials in this transition zone. nc-Si has many useful advantages over a-Si, one being that if grown properly it can have a higher [[electron mobility]], due to the presence of the silicon [[crystallite]]s. It also shows increased absorption in the red and [[infrared]] [[wavelength]]s, which make it an important material for use in a-Si [[solar cell]]s. One of the most important advantages of nanocrystalline silicon, however, is that it has increased stability over a-Si, one of the reasons being because of its lower [[hydrogen]] concentration.<sup>[citation needed]</sup> Although it currently cannot attain the mobility that poly-Si can, it has the advantage over poly-Si that it is easier to fabricate, as it can be deposited using conventional low temperature a-Si deposition techniques, such as [[Plasma Enhanced Chemical Vapor Deposition|PECVD]], as opposed to [[laser]] [[annealing (metallurgy)|annealing]] or high temperature CVD processes, in the case of poly-Si. The main application of this novel material is in the field of silicon thin film solar cells. == See also == * [[Nanoparticle]] * [[Quantum dot]] {{chem-stub}} [[Category:Silicon]] [[Category:Semiconductor materials|Silicon, Nanocrystalline]] [[Category:allotropy]] [[zh:纳米晶硅]]