Investigation of Near-Surface Chemical, Physical and Mechanical Properties of Silicon Carbide Crystals and Fibers Modified by Ion Implantation.

摘要

Modification of chemical, physical and mechanical properties of ceramic/semiconductor surfaces by ion implantation provides an opportunity to define and obtain desirable properties for a variety of applications. These include: interfaces in composite materials, electrical properties of devices and contacts, and specialized surfaces for optical waveguides, wear and corrosion resistance, etc. In this study, single crystals (6H), and whiskers of high purity silicon carbide were implanted with a variety of n- and p-type dopants (B, N, Al, P), an isovalent dopant (Ti), inert species (Ne) and hydrogen. Isochronal anneals at temperatures up to 1173K permitted systematic evaluation of thermal effects in the implanted region. Implants fluences were normalized to permit comparisons on the basis of equal concentrations of displaced Si atoms for each ion. Microstructural, mechanical and chemical effects were studied by a series of RBS/channeling, TEM, SEM, microhardness, microtensile, AES, SIMS, and wetting (sputtered and molten metal) measurements. Recovery of crystalline structure during annealing is shown to be relatively independent of the implant species but depends upon the number of atomic displacements in the Si sublattice. Near-surface mechanical and chemical effects, however, are very dependent on the chemical/electrical nature of the implanted ions. Applications to ceramic/metal interfaces in metal matrix composites are discussed.