Two kinds of amorphous Si1-xCx: H films have been prepared by the magnetron sputtering method, using ( I) a composite target of silicon and graphite in a gas mixture of argon and hydrogen, and ( II) a silicon target in a gas mixture of argon and methane. The dependence of the optical, structural, electrical and optoelectronic properties on the carbon content x has been investigated. In the case of ( I), although the formation of the carbon clusters results in the composition-independent feature

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... of the optical band gap below about x=0.5, the dark conductivity shows a minimum at about x=0.2, owing partly to the formation of SiC bonds and mainly to the decrease in the hopping conduction, which suggests the reorganization of defect-rich structure of sputter-deposited undoped amorphous Si. This phenomenon is more appreciable in the case of ( II ) where the photoconductivity for the film with about x=0.2 increases by about two orders of magnitude compared with sputter-deposited undoped amorphous Si: H.