Pressure dependence of the optical phonons and transverse effective charge in3C-SiC

Abstract

The first-order Raman spectra of $3C$-SiC have been measured as a function of hydrostatic pressure up to 22.5 GPa in a diamond anvil cell. The mode-Grüneisen parameters of the LO and TO phonons at $\Gamma$ were determined. We observed an increase of the LO-TO splitting with pressure from which an increase of the transverse effective charge upon compression results. We discuss this behavior of the transverse effective charge under lattice compression in terms of a microscopic pseudopotential calculation and of the bond-orbital model. Calculations of effective charges for other hypothetical IV-IV semiconductors are presented.