Presentation on theme: "Kinetics and Energetics of Interfacial Mixing in Co-Cu system"— Presentation transcript:
1Kinetics and Energetics of Interfacial Mixing in Co-Cu system KIMM 상변태 열역학 분과 통합 심포지움Kinetics and Energetics of Interfacial Mixing in Co-Cu systemSeung-Suk Yoo3, Sang-Pil Kim1,2, Seung-Cheol Lee1, Kwang-Ryeol Lee1 and Yong-Chae Chung21. Future Technology Research Division, KIST2. Department of Ceramic Engineering, Hanyang University3. School of Materials Science & Engineering, Seoul National University
2Motivation Interfacial Mixing for binary system Miscible system? Immiscible system? Co-Al, Co-Ti, Ni-Al, Fe-Al … Co-Cu, Fe-Cu, Fe-Ag, Fe-Au…Surface energy differenceorStrain energy difference (lattice mismatch)Co-Al system : large surface energy difference (Δγ = 60 %) large lattice mismatch (Δa0 = 14 %)Co-Cu system : Δγ = 28.5 %, Δa0 = 1.8 %
3Surface alloy formation for Co-Al * N.R. Shivaparan, Surf. Sci (2001)Co on Al (001)*4ML Co on Al(001)Low Activation BarrierIn spite of room temp. (300K) and very low incident energy of adatom(0.1eV), spontaneous surface alloy was formed. Local accelerationCo/Al(001)
4Intermixing of immiscible system C. Zimmermann et al., PRB 64, (2001).D.A. Stewart et al., PRB 68, (2003).After annealingat 750K ~ 1000K Burrowed Co nanoparticle on Cu(001) surface Interfacial mixing effects
5Computational Procedure (001) Substrate300K Initial Temperature300K Constant TemperatureFix Positionyxz1024 Substrate Atoms, 300KStep Time : 1.0 fsCase I : Co/Cu (001)Case II : Cu/fcc-Co(001)Incident Energy : 0.1eV, 1.0eV, 3.0eV, 5.0eVXMD code : MD program
6EAM Potential for Co-Cu system* Expt.Calc.a0 (Å)2.5072.51073.615Ecoh (eV)4.3864.4083.5133.538B (Gpa)180182.3140137.5γ100 (J/m2)N/A2.7892.1661.987γ1103.0512.237γ1112.5911.9531.903γ10002.7752.879γ-10103.0353.042γ11-203.7913.350* X. W. Zhou et al., Acta. Mater., 49, 4005 (2001).
7Results for low incident energy 0.1eV Co on Cu (001)0.1eV Cu on Co (001)TopView128 atoms384 atoms128 atoms384 atomsSideView Mixing Ratio : 1.56% Mixing Ratio : 0.0 %
8» Results for 5.0 eV Co on Cu (001) Cu on Co (001) Top View Side View 128 atoms384 atoms128 atoms384 atomsSideView Mixing Ratio : 21.1% Mixing Ratio : 0.78 %
9Related Factors for Mixing AnalysisRelated Factors for MixingKinetic FactorCalculate activation barrier on an interfacial mixingEnergetic FactorCheck the system energy evolutions
10Local Acceleration Phenomena* Co on Cu(001)Cu on Co(001)2.63 eV2.89 eVLocal Acceleration Contour(001) Surface* S. –P. Kim et al., J. Korean Phys. Soc., 44, 18 (2004).
11Atomic Behaviors Mixed mechanism Side view Top view Unmixed mechanism
12Kinetic Energy Evolutions K.E. of each atoms around incident atomMixed caseUnmixed caseBottom AbsorptionNO Bottom AbsorptionInduced CollisionBump UpMixing11424233
13Exchange Barrier of Intermixing MechanismCo on Cu(001)Cu on Co(001)0.553 eV1.21 eVTotal Energy Changing: eV Mixing can be happened!Total Energy Changing: eV Mixing is very difficult!
149 Cu Atoms forced Mixing on Co(001) Cont.16 Co Atoms Mixed on Cu(001)9 Cu Atoms forced Mixing on Co(001)Energy IncreaseEnergy BarrierEnergy BarrierEnergy ReductionEnergy 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)
15SummaryThrough 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 >> eVIn the case of Co on Cu is energetically stable ( eV), but Cu on Co is unstable. ( eV)