Nickel nanocrystals have received much attention for their ferromagnetic properties. The crystal properties are strongly dependent on their facets and therefore detailed study of their morphology, facets and orientation is critical for magnetic applications. In this work, equilibrium crystal shapes of self-assembled nickel nanocrystals on the (111) termination of strontium titanate (SrTiO₃) at room temperature and under ultra-high vacuum (UHV) conditions have been investigated using scanning tunneling microscope. SrTiO₃ (111) substrate was sputtered (0.5 keV, 2.5 µA, 10 min) and annealed (900°C, 1 h) under UHV conditions. Three different periodicities were observed: 2.21 ± 0.01 nm corresponding to (4 × 4) reconstruction, 3.31 ± 0.02 nm corresponding to (6 × 6) reconstruction and 2.85 ± 0.05 nm, rotated at 30° with respect to (4 × 4) reconstruction, corresponding to (3√3 × 3√3)R30° reconstruction. Nickel (∼1 ml) was deposited using an e-beam evaporator on the substrate preheated to 320°C and the sample was post-annealed multiple times. Nickel took platonic shapes of supported icosahedron comprising of (111) facets and truncated octahedron comprising of (001) and (111) facets. Based on surface energy ratios of truncated octahedrons at equilibrium, the work of adhesion was calculated to be 3.889 ± 0.167 J/m².

中文翻译：

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在 SrTiO3 (111) 载体上自组装镍二十面体和截断八面体纳米晶体

镍纳米晶体因其铁磁特性而备受关注。晶体特性在很大程度上取决于它们的晶面，因此对其形态、晶面和取向的详细研究对于磁性应用至关重要。在这项工作中，使用扫描隧道显微镜研究了室温和超高真空 (UHV) 条件下钛酸锶 (SrTiO ₃ )的 (111) 末端上自组装镍纳米晶体的平衡晶体形状。的SrTiO ₃(111) 衬底在 UHV 条件下被溅射 (0.5 keV, 2.5 µA, 10 min) 和退火 (900°C, 1 h)。观察到三种不同的周期性：2.21 ± 0.01 nm 对应于 (4 × 4) 重建，3.31 ± 0.02 nm 对应于 (6 × 6) 重建和 2.85 ± 0.05 nm，相对于 (4 × 4) 重建旋转 30° ，对应于 (3√3 × 3√3)R30° 重建。使用电子束蒸发器在预热至 320°C 的基板上沉积镍（~1 ml），并且样品经过多次后退火。镍采用柏拉图形状，由 (111) 面组成的支撑二十面体和由 (001) 和 (111) 面组成的截断八面体。根据平衡时截断八面体的表面能比，计算出的粘附功为 3.889 ± 0.167 J/m ²。