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Kinetics and Energetics of Interfacial Mixing in Co-Cu system Seung-Suk Yoo 3, Sang-Pil Kim 1,2, Seung-Cheol Lee 1, Kwang-Ryeol Lee 1 and Yong-Chae Chung.

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Presentation on theme: "Kinetics and Energetics of Interfacial Mixing in Co-Cu system Seung-Suk Yoo 3, Sang-Pil Kim 1,2, Seung-Cheol Lee 1, Kwang-Ryeol Lee 1 and Yong-Chae Chung."— Presentation transcript:

1 Kinetics and Energetics of Interfacial Mixing in Co-Cu system Seung-Suk Yoo 3, Sang-Pil Kim 1,2, Seung-Cheol Lee 1, Kwang-Ryeol Lee 1 and Yong-Chae Chung 2 1. Future Technology Research Division, KIST 2. Department of Ceramic Engineering, Hanyang University 3. School of Materials Science & Engineering, Seoul National University KIMM 상변태 열역학 분과 통합 심포지움

2 Motivation Interfacial Mixing for binary system Miscible system?Immiscible system? Surface energy difference or Strain energy difference (lattice mismatch)  Co-Al, Co-Ti, Ni-Al, Fe-Al …  Co-Cu, Fe-Cu, Fe-Ag, Fe-Au…   Co-Al system : large surface energy difference (Δγ = 60 %) large lattice mismatch (Δa 0 = 14 %)   Co-Cu system : Δγ = 28.5 %, Δa 0 = 1.8 %

3 Surface alloy formation for Co-Al In spite of room temp. (300K) and very low incident energy of adatom(0.1eV), spontaneous surface alloy was formed.  Local acceleration Co/Al(001) Low Activation Barrier Co on Al (001)* 4ML Co on Al(001) * N.R. Shivaparan, Surf. Sci (2001)

4 Intermixing of immiscible system  Burrowed Co nanoparticle on Cu(001) surface After annealing at 750K ~ 1000K C. Zimmermann et al., PRB 64, (2001).D.A. Stewart et al., PRB 68, (2003).  Interfacial mixing effects

5 Computational Procedure 300K Initial Temperature300K Constant Temperature Fix Position 1024 Substrate Atoms, 300K Step Time : 1.0 fs Case I : Co/Cu (001) Case II : Cu/fcc-Co(001) Incident Energy : 0.1eV, 1.0eV, 3.0eV, 5.0eV XMD code : MD program  y[010] x[100] z[001] (001) Substrate

6 EAM Potential for Co-Cu system* CoCu Expt.Calc.Expt.Calc. a 0 (Å) E coh (eV) B (Gpa) γ 100 (J/m 2 ) N/A γ 110 N/A γ 111 N/A γ N/A γ N/A γ N/A * X. W. Zhou et al., Acta. Mater., 49, 4005 (2001).

7 Results for low incident energy 0.1eV Co on Cu (001)  Mixing Ratio : 1.56% Top View Side View 128 atoms384 atoms  Mixing Ratio : 0.0 % 0.1eV Cu on Co (001) 128 atoms384 atoms

8 Results for 5.0 eV Cu on Co (001) 128 atoms384 atoms  Mixing Ratio : 0.78 % Co on Cu (001) 128 atoms384 atoms  Mixing Ratio : 21.1% Top View Side View »

9 Analysis Related Factors for Mixing Calculate activation barrier on an interfacial mixing Check the system energy evolutions Kinetic Factor Energetic Factor

10 Local Acceleration Phenomena* Co on Cu(001) 2.63 eV * S. –P. Kim et al., J. Korean Phys. Soc., 44, 18 (2004) eV Cu on Co(001) Local Acceleration Contour (001) Surface

11 Atomic Behaviors Mixed mechanism Side view Top view Side view Unmixed mechanism

12 Kinetic Energy Evolutions Mixing Induced Collision Bottom Absorption  K.E. of each atoms around incident atom NO Bottom Absorption Bump Up Mixed case Unmixed case

13 Total Energy Changing : eV  Mixing can be happened! Total Energy Changing : eV  Mixing is very difficult! Exchange Barrier of Intermixing eV Exchange Mechanism 1.21 eV Co on Cu(001) Cu on Co(001)

14 Cont. 16 Co Atoms Mixed on Cu(001) Energy Barrier Energy Reduction 9 Cu Atoms forced Mixing on Co(001) Energy Increase Energy Barrier   Energy Barrier for Mixing in Cu/Co(001) is 2.5 times higher than Co/Cu(001)   Effective Induced Collision happened Only in Co/Cu(001)   Kinetically Mixing can be happened in Co/Cu(001)   Kinetically Mixing hardly be happened in Cu/Co(001)

15 Summary 1. 1.Through the molecular dynamics approach, quantitative analysis in detail for atomic mixing behaviors were investigated In spite of immiscible system, interfacial mixing of Co on Cu(001) can be observed Intermixing barrier of Cu on Co(001) is much higher than that of Co on Cu.  1.21 eV >> eV 4. 4.In the case of Co on Cu is energetically stable ( eV), but Cu on Co is unstable. ( eV)


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