Interface Morphology of Metallic Multilayers by Means of Deposition Simulation
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0962-P09-03
Interface Morphology of Metallic Multilayers by Means of Deposition Simulation
K. Shintani, Y. Kometani, T. Nakajima, and Y. Yano Department of Mechanical Engineering and Intelligent Systems, University of ElectroCommunications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
ABSTRACT Growth of a Co/Cu/Co multilayer is investigated by molecular-dynamics simulation. The interactions between Co and Cu atoms are calculated in terms of the generic-embedded atom method potential. It is confirmed that two-dimensional island growth of Cu atoms on the Co substrate occurs in the simulations. The roughnesses of the surface and the interface are evaluated by means of the standard deviations of the heights of the surface and interface atoms. Intermixing atoms between the layers are also counted. We conclude that there exists an optimum combination of the incident energies of deposited Cu and Co atoms which minimizes both the roughness and intermixing of the interface. INTRODUCTION Giant magnetoresistance (GMR) devices [1] are employed as sensors for reading the magnetic data on hard disks. The devices are sandwiched structures consisting of magnetic and nonmagnetic layers. The electrical resistances of such structures vary according to whether the directions of magnetization in the magnetic layers are parallel or antiparallel. By using this characteristic, the devices can pick up the changes of magnetic fields as the changes of electric currents. In order to develop magnetic recording devices of high density, the sensitivity of GMR devices must be enhanced; the ratio of change of magenetoresistance (MR ratio) should become higher. The MR ratio depends on the quality of the interfaces between magnetic and nonmagnetic layers. In fabrication of GMR devices, therefore, it is crucial to decrease the roughness of and structural defects at the interfaces [2]. GMR devices are fabricated with molecular beam epitaxy or sputtering. Atomistic simulations are powerful tools for investigating at the nanoscale how the quality of the interfaces changes according to the physical conditions of fabrication in such methods. Wadley et al. [3] performed molecular-dynamics (MD) simulations of the growth of metallic multilayers such as Ni/Cu/Ni and Co/Cu/Co systems. Their results showed that the interfaces between the layers become smoother and intermixing of atoms increases with the increase of the energy of incident atoms. Their supercells are, however, quasi two-dimensional, and their results should be confirmed by three-dimensional simulations. We in this paper simulate the growth of Co/Cu/Co multilayers by using the MD method with three-dimensional supercells. We first examine in detail how Cu atoms deposit on the Co
z
Initial positions of adatoms
}
8.68nm
Substrate y
2.46nm
Scaling layers x
8.52nm
Fixed layer
Figure 1. Configuration of a supercell. substrate. Next, we investigate the effect of the incident energies of Cu and Co atoms on the roughness and intermixing of the interface within the resulting sandwich structur
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