Preparation Of Hydrogenated Nanocrystalline Silicon

Low-temperature fabrication process can be required for thin-film transistors and photovoltaic cells with inexpensive substrates. The following preparation techniques have been used to achieve it: (i) plasma-enhanced chemical vapor deposition (PECVD) of silane (SiH4) gas diluted in H2 gas, (ii) thermocatalytic or hot-wire assisted chemical vapor deposition (HWCVD) of SiH4 gas diluted in H2 gas, and (iii) pulsed laser crystallization (PLC) of amorphous silicon films. These techniques are summarized below.

2.1. Plasma-Enhanced CVD

This method has been well established in depositing hydro-genated amorphous silicon films (a-Si:H) and hence we only modify the deposition conditions to prepare nanocrystalline silicon (nc-Si:H) [1-5]. The structural compositions of nc-Si:H vary by changing the deposition conditions, that is, the silane to hydrogen ratio and the plasma excitation frequency. Unlike a-Si:H deposition, decrease of the silane to hydrogen gas ratio (less than 2% in gas ratio) is required to increase volume fraction of crystalline. It should be noted that the material prepared by PECVD is a phase mixture of amorphous and crystalline regions. The substrate

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Encyclopedia of Nanoscience and Nanotechnology Edited by H. S. Nalwa Volume 4: Pages (35-41)

Grain cluster (Region A)

20 nm

Disorder (Region B)

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