1 / 14

Molecular Dynamics Simulation to understand the Interfacial Structure of Thin Films

Molecular Dynamics Simulation to understand the Interfacial Structure of Thin Films. Sang-Pil Kim and Kwang-Ryeol Lee Computational Science Center Korea Institute of Science and Technology. Devices with Thin Multilayers. 1~2nm. Spin valve for magnetic devices. Major materials issue is the

payala
Télécharger la présentation

Molecular Dynamics Simulation to understand the Interfacial Structure of Thin Films

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Molecular Dynamics Simulation to understand the Interfacial Structure of Thin Films Sang-Pil Kim and Kwang-Ryeol Lee Computational Science Center Korea Institute of Science and Technology

  2. Devices with Thin Multilayers 1~2nm Spin valve for magnetic devices Major materials issue is the interfacial structurein atomic scale

  3. Calculation Procedure Adatom (normal incident  0.1 eV) 300K Initial Temperature 300K Constant Temperature Fixed Atom Position • Co-Al EAM potential • x,y-axis : Periodic Boundary Condition • z-axis : Open Surface • MD time step : 1.0 fs R. Pasianot et al, Phys. Rev. B45, 12704 (1992). A. F. Voter et al , MRS Proc. 82, 175 (1987). C. Vailhe et al, J. Mater. Res. 12, 2559 (1997).

  4. Deposition in Co-Al system Deposition energy = 0.1 eV Co on Al (001) Al on Co (001)

  5. Conventional Concepts Ultra thin film Substrate is not a static media but an active media!

  6. Asymmetry in Interfacial Mixing 3ML Al on Co (001) 8ML Co on Al (001)

  7. Energy Barrier for Intermixing Incorporation energy barrier calculation by using DFT Surface intermixing could not be happened such a low incident energy of adatom(0.1eV) C. Kim et al., J Korean Phys. Soc. (2004).

  8. Local Acceleration Effects As the depositing atom approaches to the substrate, the kinetic energy of adatom increases very rapidly at the vicinity of the substrate surface.  “Local Acceleration Effect*”

  9. Local Acceleration Deposition energy = 0.1 eV Co on Al (001) Al on Co (001)

  10. Contour of Local Acceleration Co on Al (001) Al on Co (001) Energy barrier for atomic penetration

  11. Experimental Evidences Coaxial Impact Collision ion Scattering Spectroscopy (CAICISS) Al on Co (0001) Co on Al (001) Only in the case of deposition Co on Al sub., surface structure was changed.  Experimental evidence of asymmetric intermixing behavior

  12. Spin-Up Spin-Down Magnetic Property Calculation Nonmagnetic behavior Magnetic behavior B2 - CoAl Ab-initio calculations B2 - CoAl FCC - Al HCP - Co Nonmagnetic Metal Nonmagnetic Metal Magnetic Metal  The perfectly ordered B2-CoAl does not show any magnetic behavior

  13. Experimental Evidences Asymmetric Magnetic Behaviors in Co-Al system • Co/Co(3nm)/Cu/Si subs. Reference sample • Cu/Al(3nm)/Co(3nm)/Cu/Si subs. Al/Co case • Cu/Co(3nm)/Al(84nm)/Si subs. Co/Al case • Only in the Co/Al case, magnetism was reduced by interfacial mixing. • Hysteresis loop cannot be observed when the thickness of Co was smaller than 1 nm or 3 atomic layers, which agrees well with the MD results

  14. Conclusions • The asymmetry of the surface intermixing during thin film growth can be understood by comparing the local acceleration effect with the energy barrier for mixing. • CAICISS & MOKE results were clearly shown the asymmetric intermixing as predicted in MD simulations. • Magnetism of B2-CoxAl1-x alloy was exhibited only for the Co concentration higher than 50 atomic %.

More Related