We review the growth behavior of epitaxial ZrB2(0001) films on Si(111) via the thermal decomposition of the unimolecular precursor Zr(BH 4)4 studied in situ by low-energy electron diffraction and low-energy electron microscopy, and ex situ by cross-sectional transmission electron microscopy and atomic force microscopy. Under appropriate kinetic conditions, epitaxy was achieved in spite of the very large lattice mismatch between ZrB2(0001) and Si(111). The growth was followed from the initial nucleation stage to the final epitaxial film at various growth temperatures. At 900°C, the growth of ZrB2(0001) proceeded by the nucleation of two-dimensional islands. These islands eventually coalesced to form a continuous atomically smooth film. The interface between ZrB 2(0001) and Si(111) was modeled theoretically and the most favorable interface consisted of the ZrB2(0001) growing on a Si(111)-(√3 × √3)B surface with the Zr layer nearest to the interface and the B layer on the top surface. The in-plane a lattice parameter of the ZrB 2(0001) surface has a perfect match with that of Al xGa1-xN where x = 0.26. Epitaxial layers of Al 0.2Ga0.8N grown on a ZrB2/Si(111) substrate by metalorganic chemical vapor deposition (MOCVD) exhibit luminescence properties comparable to or better than those from layers of identical composition grown on sapphire substrates. © 2005 THE PHYSICAL SOCIETY OF THE REPUBLIC OF CHINA.