Epitaxial film growth of zirconium diboride on Si(0 0 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 ZrB ₂, 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 [1 1 0 0 ] direction, i.e. [1 1 0 0]ZrB2//[001]Si, the epitaxy produces two orthogonal domains as the result of a 6:5 misfit for [1 1 2 0]ZrB2//[1 1 0]Si and a 13:12 misfit for [0 0 0 1;]ZrB2//[1 1 0]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.