SILICON FIBERS PRODUCED BY HIGH-PRESSURE LCVD

Using a unique fiber-growth control mechanism and high-reaction pressures (> 1 bar), silicon fibers were grown by laser-assisted chemical vapor deposition (LCVD) from silane near the focal point of a cw Nd:YAG laser beam. Fiber-growth rates ranged from < 1 to 500 mum/s and fiber tip temperatures from 525 to 1412-degrees-C. At low fiber-tip temperatures (< 600-degrees-C) silicon fibers yielding glassy fracture were obtained. Some crystallinity was observed by X-ray diffraction. Polycrystalline silicon fibers were formed at intermediate temperatures, single-crystal silicon fibers at high-laser intensities and high-tip temperatures. The single crystal LCVD silicon fibers were formed by a vapor-liquid-solid (VLS) mechanism. Single-crystal VLS-LCVD silicon fibers were also obtained from liquid silicon-metal alloys by initiating fiber growth from the end of thin palladium, gold and platinum wires.