Laser assisted fiber growth
AssigneeClemson University
InventorPaul C. Nordine
Life of this patent
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Abstract
A method of making pure fibers from a parent material utilizing laser energy. A short wavelength laser is used to achieve a diffraction limited focal spot diameter that is smaller than the diameter of the growing fiber. Focused laser beam convergence is used to obtain a fiber growth rate that depends on the fiber tip portion such that the fiber growth rate achieves a value equal to the controlled fiber pulling rate. The present invention achieves vapor-liquid-solid growth of single crystal silicon fibers and whiskers from silane gas and permits the use of other materials in the production of fibers by the vapor-liquid-solid process. The method provides an increase in the allowable ambient pressure and growth temperature and a large and more energy efficient growth velocity as compared to carbon dioxide based laser beam technology.
Claims27
A method of making pure fibers from a parent material, comprising the steps of:
- (a) placing a substrate in a gaseous environment wherein the gaseous environment includes the parent material in a gaseous form;
- and
- (b) heating the substrate with an emitted laser beam such that formation of a continuous, substrate free fiber growth is initiated and maintained, the fiber growth being supplied by accretions of the parent material from the gaseous environment.
A method of producing a ribbon, comprising the steps of:
- (a) placing a substrate in a gaseous environment, the gaseous environment containing some proportion of the parent material;
- (b) introducing an emitted laser beam into the gaseous environment;
- (c) focusing the emitted laser beam to a relatively small region, the region thereby encountering relatively elevated temperatures as compared to the remainder of the gaseous environment, the region being so positioned as to intercept the substrate, thereby causing the initiation of the formation of a continuous, substrate free fiber from the gaseous environment onto the substrate;
- (d) translating the region in an oscillatory motion thereby causing the accretion of a ribbon having a width corresponding to a distance traveled by the region during one half cycle of the oscillatory motion;
- and
- (e) simultaneously translating the region in a continuous direction and at a velocity substantially less than the oscillatory motion, the translation in a continuous direction defining the longitudinal axis of the ribbon.
A method of producing a ribbon, comprising the steps of:
- (a) placing a substrate possessing relatively low thermal conductivity in a gaseous environment, the gaseous environment including some proportion of the parent material;
- (b) introducing an emitted laser beam into the gaseous environment;
- (c) passing the emitted laser light through a cylindrical lens, the cylindrical lens creating a region of elevated temperature, the region being characterized as a thin longitudinal area having a length;
- (d) focusing the longitudinal region so as to intercept the substrate, thereby initiating an accretion of the parent material from the gaseous state onto the substrate, the ribbon having a width corresponding to the length of the longitudinal region;
- and
- (e) translating the region of elevated temperatures in a continuous direction, the continuous direction defining the longitudinal axis of the ribbon produced.
Dependencies are inferred from the claim text.