Nanocrystalline silicon

Nanocrystalline silicon (nc-Si) is similar to amorphous silicon (a-Si), in that it has an 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 (uc-Si). The difference comes solely from the grain size of the cystalline grains. Most materials with grains in the micron range are actually fine-grained polysilicon, so nanocrystalline silicon is a better term.

nc-Si has many useful advantages over a-Si, one being its higher mobility, due the the prescence of the silicon crystallites. It also shows increased absorption in the red and infrared wavelengths, which make it an important material for use in a-Si solar cells. Although it currently cannot attain the mobilities seen in poly-Si, it has the advantage over poly-Si that it is easier to fabricate, as it can be deposited using conventional a-Si deposition techniques, such as PECVD.