The solid solutions of rebulite and jankovićite in the phase system Tl2S-As2S3-Sb2S3

Syntheses along the Tl₅(As,Sb)₁₃S₂₂ compositional line in the Tl₂S-As₂S₃-Sb₂S₃ phase system showed that the compositional range of rebulite extends from Tl₅As_9.5Sb_3.5S₂₂ to Tl₅As_7.75Sb_5.25S₂₂. The Sb-rich end-member is in equilibrium with jankovićite of ideal composition Tl₅Sb_7.5As_5.5S₂₂. It is considered to be the As-rich end-member of the jankovićite solid solution. The crystal structure analyses of crystals from the As and Sb end-members of rebulite show that the Sb/As substitution is present in Sb3, Sb4, Sb5, As1 and As2 structural sites. Of them, Sb3 is always Sb dominated whereas other four vary from As- to Sb-dominated over the range of the solid solution. The change of the structural topology from jankovićite to rebulite, the closely related but not identical structures, is explained through necessity to accommodate the smaller volumes of the As coordination polyhedra and is accomplished through unit-cell twinning over the periodic (001)_reb twin boundaries. The As end-member of the rebulite solid solution is in equilibrium with the phase of Tl_2.4Sb_0.68As_7.18S₁₃ ideal composition, interpreted as imhofite.

Cubic (Mg,Zn)O Nanowire Growth Using Catalyst-Driven Molecular Beam Epitaxy

We report on the growth of Mg-rich cubic (Mg,Zn)O nanowires using a catalysis-driven molecular-beam-epitaxy method. Nanowires were grown on both Si and Al2O3 substrates coated with a nominally 2-nm-thick layer of Ag. The (Mg,Zn)O nanowires were grown with a Zn and Mg cation flux, with an O2/O3 mixture serving as the oxidizing species. The growth temperature was 400 °C. Under these conditions, nanowires were observed to grow on the Ag sites. The nanowire diameter was on the order of 90 nm. (Mg,Zn)O nanowires as long as 2 μm were realized. High-resolution transmission electron microscope imagery shows the nanowires had single-phase cubic rock salt structure (Mg,Zn)O with a growth direction along the [100]. The presence and compositional distribution of Mg and Zn in the single nanowire were confirmed using a compositional line-scan, profiled across the nanowire, by energy dispersive spectrometry with scanning transmission electron microscopy.