Very thin diamond films (thickness ∼0.1 &mgr;m) have been investigated by x‐ray diffraction pole figure measurements using synchrotron radiation in order to understand the mechanism of heteroepitaxial diamond nucleation and the first steps of film growth on silicon(001) substrates. The diamond layers consist of an epitaxially aligned component with a crystallographic orientation identical to the substrate. The initial orientational spread of the grains around the perfect epitaxial orientation prior to any modification by a subsequent textured growth step has been determined. In the studied temperature range for the nucleation step the misalignment decreases slightly with increasing temperature. Besides the epitaxial crystallites their corresponding twins of first and second order have been found. The intensity distribution of the pole figures indicates that the process of twinning plays a dominating role in the initial growth stage which shows a tendency to become even more pronounced for higher substrate temperatures. ©1996 American Institute of Physics.