Patent ID: 8778719

Claim:
A method, comprising: producing a linear semiconductor substrate that includes a linear core with a semiconductor thin film formed on an outer surface of the linear core, by: reducing a surface of a spun fiber, to form the linear core, in a fiber-drawing method comprising: melting a glass parent material worked into a desired shape within a heating furnace and spinning the material, or melting a glass raw material within a heated crucible and spinning the material, to thereby produce a fiber; withdrawing the spun and produced fiber by a withdrawer while controlling a withdrawing speed of the fiber, or a feeding speed of the parent material, or both, so that the fiber has a constant outer diameter; and winding up the fiber by a winder, depositing a semiconductor onto the outer surface of the linear core to form the semiconductor thin film, and growing a size of a crystal grain of the semiconductor that forms the semiconductor thin film by passing the semiconductor thin film through an ambience including a temperature distribution with a temperature lowered in a fiber-drawing direction from a temperature at or higher than a melting point of the semiconductor thin film, wherein the growing the size of the crystal grain is performed during the fiber-drawing method or during another step to thereby bring a grain diameter of the crystal grain to Φ40 microns or more.