We recently showed that r-B4C can be epitaxially grown using chemical vapor deposition (CVD) with triethylborane (TEB, B(CH2CH3)3) as a single source precursor and 4H-SiC as substrates at 1300 °C. The B4C films grew epitaxially on the (0001 ̅ ) surface of 4H-SiC, commonly known as the C-face 4H-SiC, with the in-plane epitaxial relationship: B4C(0001)[101 ̅ 0]∥ 4H-SiC(0001 ̅ )[101 ̅ 0]. In contrast, the film growing on the (0001) 4H-SiC, also known as the Si-face 4H-SiC, was polycrystalline. From the literature, we note that epitaxial growth of r-B4C on the Si-face of 4H-SiC substrates by CVD has been reported. But this CVD process used BCl3 and C3H8 as precursors and 4° off-axis 4H-SiC substrates and required pretreatment of the surface with BCl3 to form an amorphous boron layer, which was converted to r-B4C upon CVD with BCl3 and C3H8 at 1600 °C. Without the pretreatment, the BxC growth on the Si-face of 4H-SiC was also polycrystalline. Epitaxial B4C growth on 4H-SiC (0001 ̅ ) has also been reported using pulsed lazer deposition. Following our results , we now seek to understand, at an atomic level, the cause of the differences between the films grown on the two faces of 4H-SiC. We employ advanced (scanning) transmission electron microscopy ((S)TEM) techniques to explore the grown films.