The surface morphology and crystallinity of homoepitaxially grown (111), (001), and (110) diamonds were comparatively investigated by using low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED). We found that the crystal quality and the surface smoothness of the homoepitaxial diamond on (111) strongly depends on the substrate temperature; the highest quality homoepitaxial diamond on (111) can be successfully grown at 690 degrees C. The highest quality homoepitaxial diamond had the smoothest C(111)-1 X 1 surface, which was evidenced by the first observation of sharp and clear Kikuchi patterns, comparable, to those of a C(001) surface. Caution has to be exercised when judging the structure of a C(111) surface from a LEED(1 X 1) pattern, because its observation can encompass surface morphologies ranging from single-crystal to polycrystalline diamonds. In contrast, surface roughness has a dramatic effect on the. RHEED diffraction pattern. In the smoothest C(001)- 2 X 1/1 X 2 surface, the RHEED pattern shows spots rather than streaks. Growth on a (110) diamond surface results in {111}-oriented microfacets.