Magnetic and electrical properties of Fe∕Si core-shell cluster assemblies prepared with double-glow-discharge sources

Abstract

Using a double glow-discharge-cluster-source-system, in which one glow discharge is a dc mode and the other an rf discharge mode, Fe and Si clusters have been produced independently and deposited simultaneously on a substrate. When a separation plate is not inserted between two glow-discharge chambers, core-shell clusters are obtained: An Fe core is surrounded by small Si crystallites. The magnetization measurement indicates that the magnetic coercive force of the Fe∕Si core-shell cluster assembly is much smaller than those of Fe cluster assemblies at low temperature and no shift of the field-cooled hysteresis loop related to the zero-field-cooled loop is detected, probably because Si shells prevent Fe cluster surfaces from their oxidation. The temperature dependence of electrical resistance is attributed to electron conduction via Si shell networks above 180K, while it is attributed to variable range electron conduction between Fe clusters.

Fe/Ni Cluster Hybrid Material Produced by Double Glow Discharge Sources

“…By inserting a separation plate between two glow-discharge rooms, small Co and Fe clusters were distributed at random together with the Si and Al clusters which were agglomerated to form large secondary particles, while partially alloyed Fe-Ni clusters were obtained on substrates. Without inserting the separation plate, core-shell morphologies were obtained for Co/Si, Fe/Si and Fe/Al cluster hybrids, in which Co or Fe cores were surrounded by small Si or Al crystallites, [10][11][12][13] while heterogeneous alloy phases for Fe/Ni cluster hybrids. 14) Since the second PGCCD apparatus was also a hollow cathode type and two different metal plates could be set on the two target holders of the single glow discharge chamber, we prepared Co/Pd, Nb/Ag and Fe/Ni cluster hybrids by supplying electric powers independently to these two targets.…”

“…10) When two glow discharges were divided by inserting a separation plate, two kinds of vapor atoms were sputtered out of the targets. Using this second PGCCD system, Co/Si, 10,11) Fe/Si, 12) and Fe/Al 13) and Fe/Ni 14) cluster hybrids were prepared on substrates. By inserting a separation plate between two glow-discharge rooms, small Co and Fe clusters were distributed at random together with the Si and Al clusters which were agglomerated to form large secondary particles, while partially alloyed Fe-Ni clusters were obtained on substrates.…”

Electrical Resistivity and Morphology of Sn_1&minus;<i>_x</i>/Si<i>_x</i> Core&ndash;Shell Cluster Network Prepared by a Plasma-Gas-Condensation Cluster Source

“…It can vaporize refractive metals and control cluster size by adjusting sputtering power and gas pressure. We have succeeded in producing Fe/Si, 7) Co/Si 8) and Fe/Al, 9) core shell clusters by a double-source PGCCD apparatus and Co/CoO, 10) coreshell clusters by a single source PGCCD apparatus with a delicate oxidation process. The core parts of those coreshell clusters are thermally and chemically stable and give rise to additional properties: 10,11) semiconducting and tunneling conductivities, and a quantum tunneling type magnetic relaxation were observed.…”

Core-Shell Formation and Juxtaposition in Fe and Si Hybrid Clusters Prepared by Controlling the Collision Stages

“…When their collision stages are delayed with the setting of a partition plate, Fe or Co clusters can be randomly juxtaposed with Al, Si or Ni clusters, where Al and Si clusters are amorphous. [5][6][7][8][9] On the other hand, when their collision stages are expedited without setting the partition plate, core-shell clusters, in which Fe or Co cores are surrounded by amorphous Si or Al shells, and alloy clusters, in which Fe and Ni are mixed with each other, can be obtained, [5][6][7][8][9] depending on the combination of materials.…”