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]]