Low temperature synthesis of silicon fibers

#1. Field of the Invention

#The invention relates to the field of providing a synthesis technique to grow bulk quantities of semiconductor nanowires at temperatures less than 500° C.

#2. Description of the Prior Art

#A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts throughout the several views and wherein:

#FIG. 1 shows a multitude of nanowires. These fibers were grown with H2/N2 ratio of 0.005, pressure of 30 Torr and microwave power of 1000W;

#FIG. 2 shows silicon nanofibers for short time scale growth (initial one hour);

#This invention provides a novel synthesis route for growing one-dimensional structures of semiconductor materials in wire, whisker and rod shapes at temperatures well under 550° C., preferably less than 300° C. This low-temperature synthesis is made possible by the use of gallium as a preferable absorption site. Gallium has a low melting temperature (˜30° C.) and broad temperature range for the melt phase (30–2400° C. at 1 atm). Indium, which has a melting temperature of 156.6° C., and a melt range of 156.6 to 2000° C., is also useful as a dissolution medium. In one embodiment of the invention of the invention, growth of silicon fibers was observed when silicon substrates covered with a thin film of gallium were exposed to mixture of nitrogen and hydrogen in a microwave-generated plasma. The resulting silicon wires ranged from several microns to less than ten (10) nanometers in diameter. The observed growth rates were on the order of 100 microns/hour. Results indicate that this technique is capable of producing oriented rods and whiskers with narrow diameter distributions. The growth mechanism in this method is hypothesized to be similar to that in other VLS process, i.e., rapid dissolution of silicon solute in gallium melt, formation of nuclei, nuclei surfacing out of the gallium melt, growth of silicon in one dimension in the form of fibers.

#This technique offers several advantages over conventional VLS techniques using silicon-transition metal eutectic for catalyzed growth. When the desired fibers comprise silicon or germanium, there is no need to supply silicon or germanium in solid form. Secondly, the very low temperatures required when using gallium as the dissolution medium allows easier integration with other processing techniques and materials involved in electronics and opt-electronic device fabrication. Nanometer scale one-dimensional semiconductor structure such as nanowires and nonwhiskers are expected to be critically important in advanced mesoscopic electronic and optical device applications.

#The advantage of low-temperature fabrication are also useful for those semiconductors in which the substrate and the fibers differ in composition. In such case, both or all fibers components may be provided in the vapor phase.