Image Number 11 for United States Patent #6593164.
A cyano process of introducing cyano ions (CN.sup.-) into an amorphous silicon layer is performed after the amorphous silicon layer has been formed over a substrate or after the layer has been exposed to light. For example, the substrate is immersed in an aqueous solution containing potassium cyanide (KCN) in a vessel. The cyano process eliminates factors (e.g., weak bonds, defects, and centers of recombination) of decrease in photoconductivity of the as-deposited amorphous silicon thin film, which are identifiable in the as-deposited film. As a result, the photoconductivity of the amorphous silicon layer is already higher than usual from the beginning and will hardly decrease even upon exposure to light.