A comparative study is performed of the properties of SiC films, grown in the presence and absence of a Si1-xGex interfacial layer on top of a Si(111) substrate with x = 0.23. The SiC film growth is carried out at 960 degrees C by carbonization of the substrates with a solid carbon source using molecular beam epitaxy, leading to void formation at the SiC/substrate interface. The film properties have been investigated by transmission electron microscopy, x-ray diffraction, Rutherford backscattering spectrometry, and atomic force microscopy. The results show that the presence of the Si1-xGex layer improves the crystal quality and surface smoothness.