INFRARED-ABSORPTION OF BETA-SIC PARTICLES PREPARED BY CHEMICAL VAPOR-DEPOSITION

Infrared absorption characteristics of β-SiC particles prepared by chemical vapour deposition were studied. These particles were either solid or had a silicon core and/or were hollow. The solid particles exhibited a single absorption peak between the transverse optical frequency (ωTO = 794 cm-1) and the longitudinal optical frequency (ωLO = 976 cm-1) of β-SiC. This absorption peak shifted to a lower frequency with increasing lattice parameter of β-SiC and increasing free silicon content. The particles containing a silicon core and/or were hollow exhibited double absorption peaks close to ωTO and ωLO. The peak at the LO side shifted to a lower frequency and that at the TO side to a higher frequency with decreasing silicon core size and increasing hollow size. Using the calculations based on the effective medium theory assuming surface phonon mode, the relationship between the infrared absorption characteristics and microstructures of the β-SiC particles are explained. © 1990 Chapman and Hall Ltd.