GROWTH OF NICKEL-OXIDE SINGLE-CRYSTALS AND BICRYSTALS VIA CHEMICAL-VAPOR TRANSPORT

A chemical vapor transport (CVT) method was successfully used to grow NiO single crystals and bicrystals heteroepitaxially on single-crystal MgO substrates. The most favorable growth conditions were obtained at 1400 K using 250 torr (similar to 3.33 x 10(4) Pa) of HCl(g) as the t ransport agent, Average growth rates greater than 100 mu m/h were easi ly achieved under these conditions. The CVT-grown NiO single crystals and bicrystals usually displayed highly reflective facets along the gr owth direction that suggest high mechanical quality. The grain boundar ies in the bicrystals were observed to be perpendicular to the (001) g rowth surface. The epitaxial NiO crystals were easily separated from t he MgO substrate by dissolving away the latter in 85% H3PO4 at 190 deg rees C. The crystallinity and purity of the deposits were checked usin g these free-standing NiO crystals. The concentration of cation impuri ties and the Cl content in the CVT-grown crystals were investigated by inductively coupled plasma (ICP) mass-spectrometric analysis and neut ron activation analysis, respectively. High-resolution transmission el ectron microscopy of a Sigma 13 (510) boundary revealed a structure at the atomic scale that provided no evidence for segregated phases.