Small-scale high-strength silicon carbide fibers fabricated from thin films produced by plasma-enhanced chemical vapor deposition

Microfabrication technology has been used to produce free-standing SixC1−xHy fibers of precisely controlled geometry and composition from thin films deposited by PECVD. The films were deposited in a parallel plate reactor from a mixture of SiH4 and CH4. The atomic composition of the films was determined using RBS and forward recoil spectroscopy (FRES). The film composition was varied from x=0.2–0.8 by adjusting the gas flow, the plasma frequency (30 kHz or 13.56 MHz), and plasma power. The films deposited at 300 °C contained from 33 to 50 at. % of hydrogen. The density, internal stress and refractive index of the films were measured. These properties were strongly dependent on gas flow ratio and plasma frequency. The lower frequency plasma yielded denser and higher compressive stress material with higher refractive index. Photolithography and reactive ion etching techniques were used to pattern the films into one centimeter long self-supporting fibers with cross-sectional areas in the gauge section ranging from 1 to 2 μm2. Tensile strength and elastic modulus measurements of these fibers were used to evaluate the films. Fibers with an average tensile strength of up to 2.9 GPa were obtained, suggesting a novel way to produce high strength SiC fibers of controlled geometry and composition.