Nucleation and growth of epitaxial ZrB2(0001) on Si(111)

The growth behavior of epitaxial ZrB2(0001) films on Si(111) via the thermal decomposition of the unimolecular precursor Zr(BH4)4 was studied in situ using low-energy electron diffraction and low-energy electron microscopy, and ex situ using 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). Our study followed the growth from the initial nucleation stage to the final epitaxial film at various growth temperatures. At 900 deg C, the growth of ZrB2(0001) proceeded by the nucleation of two-dimensional islands. These islands eventually coalesced to form a smooth film with an RMS roughness of 0.9nm. The interface between ZrB2(0001) and Si(111) was modeled theoretically and the most favorable interface consisted of the ZrB2(0001) growing on a Si(111)-({square root}3X{square root}3)B surface with the Zr-layer nearest to the interface and the B-layer on the top surface. Author