Probing optical, phonon, thermal and defect properties of 3C–SiC/Si (001).

Comprehensive results of experimental and theoretical studies are reported to probe the optical, phonon, thermal and defect properties of 3C–SiC/Si (001). By exploiting phonon-assisted Raman scattering (RS) spectroscopy we have recognized, among the conventional optical modes [TO(Γ) ~ 796 cm − 1 and LO(Γ) ~ 973 cm − 1 ], two extra phonon features near ~ 625 cm − 1 and 670 cm − 1 — possibly falling between the forbidden gap of the acoustic and optical branches. Temperature dependent profile of the unresolved ~ 670 cm − 1 band has indicated disordering by nearby defects and/or stress — rendering shorter phonon lifetime to instigate mode broadening. Accurate assessments of the lattice dynamical, thermal and defect properties are achieved by exploiting phonons from a rigid-ion model fitted to the inelastic x-ray scattering data and expending apposite group-theoretical selection rules. Lattice relaxations around Si/C atoms attained by the first-principles bond-orbital model for isolated defects have helped us to evaluate the necessary force constant variations for constructing perturbation matrices of the “complex-defect-centers”. For isolated anti-site C Si and Si C defects ( T d -symmetry), our methodical Green's function (GF) theory has predicted triply degenerate F 2 gap modes near 630 cm − 1 and 660 cm − 1 , respectively. The GF simulations of impurity vibrations for a neutral nearest-neighbor anti-site Si C –C Si pair-defect ( C 3v -symmetry) provided gap-modes to appear within the broad ~ 670 cm − 1 band at 664.8 cm − 1 ( a 1 ) and 660.6 cm − 1 ( e ). The calculated results of localized vibrational modes are compared and discussed with phonon features observed in the RS experiments as well as with the density function theory. [ABSTRACT FROM AUTHOR]