Isomers of the Cu5 cluster: a density function theory study

In this work,a systematic study of some possible isomer structures of the Cu 5 cluster obtained from density functional theory methods is presented.The polarisation and pseudopotential basis sets are employed in the calculations.The results show that the binding energies,frequencies,coordination numbers and average bond lengths are in reasonable agreement with reported experimental data.Moreover,four isomers of the Cu 5 cluster are obtained according to calculations,in which the most stable configuration is the planar structure.Meanwhile,two three-dimensional structures of the Cu 5 cluster are obtained in this work,which might be valuable for further theoretical and experimental studies.In addition,our study proves the possibility of the isomer structures of the Cu 5 cluster.     

Co+离子注入单晶TiO2铁磁性来源与微结构研究

在室温下,将能量为80 keV, 注量分别为1×1016和1×1017ions/cm2的Co+离子注入到10 mm×10 mm×0.5 mm的单晶TiO₂样品。在氮气保护下, Co+离子注量为1×1017 ions/cm2时样品在温度为900 ℃的条件下退火30 min。 利用超导量子干涉仪 （SQUID）测量样品磁性, 并应用X射线衍射（XRD）和扩展边X射线吸收精细结构谱（EXAFS）研究Co+离子注入后样品的微观结构。 样品磁性测量结果表明:Co+离子注入后的样品具有室温铁磁性, 并且其饱和磁化强度的大小与Co+离子注量及样品是否经退火处理有关。 EXAFS研究表明: Co元素在Co+离子注量为1×1017ions/cm2的样品中主要以团簇形式存在;样品经退火处理后, Co团簇消失, 并发现Co部分替代TiO₂单晶中的Ti。Co+离子注入后, 在样品中形成Co团簇与否受离子注量的影响。 阐述了样品微观结构与铁磁性来源之间的关系。 At room temperature, monocrystalline plates of rutile (TiO₂) were implanted with cobalt ions of an energy of 80 keV to fluences of 1×1016 and 1×1017 ions/cm2 respectively . The 1×1017 ions/cm2 Co implanted samples were annealed in nitrogen at 900 ℃ for 30 min. The magnetic properties of Co implanted samples were measured with a superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the X ray diffraction (XRD) and Extended X ray Absorption Fine Structure (EXAFS) were applied to investigate the structural and compositional properties of Co implanted samples. The magnetic measurements of samples showed that the size of the saturation magnetization of the Co implanted samples were related to the fluence of ions, and the saturation magnetization of the sample after annealed decreased significantly. The EXAFS measurements showed the presence of cobalt metallic clusters in the sample implanted to ion fluence of 1×1017 ions/cm2. The Co metallic clusters disappeared in the sample after annealed, and resulted in the oxidized Co, which is presumed to substitute into the Ti site. The formation of Co clusters or not was determined by the ion fluence. The relation between ferromagnetic behavior and microscopic structure of the Co implanted samples is discussed.     

Cluster size and substrate temperature affecting thin film formation during copper cluster deposition on a Si （001） surface

The soft deposition of Cu clusters on a Si(001) surface was studied by molecular dynamics simulations.The embedded atom method,the Stillinger-Weber and the Lennar-Jones potentials were used to describe the interactions between the cluster atoms,between the substrate atoms,and between the cluster and the substrate atoms,respectively.The Cu13,Cu55,and Cu147 clusters were investigated at different substrate temperatures.We found that the substrate temperature had a significant effect on the Cu147 cluster.For smaller Cu13 and Cu55 clusters,the substrate temperature in the range of study appeared to have little effect on the mean center-of-mass height.The clusters showed better degrees of epitaxy at 800 K.With the same substrate temperature,the Cu55 cluster demonstrated the highest degree of epitaxy,followed by Cu147 and then Cu13 clusters.In addition,the Cu55 cluster showed the lowest mean center-of-mass height.These results suggested that the Cu55 cluster is a better choice for the thin-film formation among the clusters considered.Our studies may provide insight into the formation of desired Cu thin films on a Si substrate.