Epitaxial film growth of zirconium diboride on Si(0Â 0Â 1)

The structure of epitaxial ZrB2 films grown on Si(0 0 1) substrates via the thermal decomposition of the unimolecular precursor Zr(BH4)4 was studied by X-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy (XTEM). In spite of the large lattice mismatch between the Si(0 0 1) substrate and ZrB2, epitaxy occurs via a coincidence-misfit mechanism in which the strain between film and substrate is accommodated by edge dislocations along the film-substrate interface. While the growth axis of the ZrB2 film lies along the [11̲00] direction, i.e. [11̲00]ZrB2//[001]Si, the epitaxy produces two orthogonal domains as the result of a 6:5 misfit for [112̲0]ZrB2//[11̲0]Si and a 13:12 misfit for [0001̲]ZrB2//[11̲0]Si along the same direction on the interface plane. These domains take the form of two-dimensional rectangular islands orthogonal to each other. The island-substrate and island-island interfaces were examined in detail with high-resolution XTEM and compared with theoretical models.