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

Abstract

The structure of epitaxial ZrB 2 films grown on Si(0 0 1) substrates via the thermal decomposition of the unimolecular precursor Zr(BH 4) 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 ZrB 2 film lies along the [ 1 1 ̲ 0 0 ] direction, i.e. [ 1 1 ̲ 0 0 ] ZrB 2 / / [ 0 0 1 ] Si , the epitaxy produces two orthogonal domains as the result of a 6:5 misfit for [ 1 1 2 ̲ 0 ] ZrB 2 / / [ 1 1 ̲ 0 ] Si and a 13:12 misfit for [ 0 0 0 1 ̲ ] ZrB 2 / / [ 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.