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We present experimentally determined biaxial strain coefficients for the longitudinal optical ͑LO͒ and transversal optical ͑TO͒ Raman lines in 3C-SiC. Suspended 3C-SiC membranes with a ͑100͒ texture are deflected by a variable pressure load on one side and the strain-induced shifts of the LO and TO Raman lines are measured while the strain is simultaneously calculated from the membrane deflection vs pressure. Using these results we measure the residual strain of 3C-SiC films grown on Si as a function of preparation conditions. The largest residual strain is found in thin samples which relaxes as film thickness increases to a value imposed by the different thermal expansion coefficients of 3C-SiC and Si. As the residual strain decreases and the film thickness increases, the Raman lines narrow indicating an improved crystalline quality. We also find a reduction of the residual strain with increasing growth rate.

The width of phonon lines in the Raman spectra of ideal isotopically pure solids is determined by inelastic scattering processes. In solids that contain a mixture of different isotopes of one atomic constituent, elastic scattering due to isotopic mass disorder opens up decay channels that result in additional line broadening. We use different polytypes of SiC with an associated number of Raman active modes in order to experimentally validate the proportionality between linewidth and phonon density of states predicted by a simple elastic scattering theory.

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