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Transcript of Atomic Scale Computational Simulation for Nano-materials and Devices: A New Research Tool for...
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Atomic Scale Computational Simulation for Nano-materials and Devices: A New Research Tool for NanotechnologyKwang-Ryeol Lee
Future Technology Research Division, KIST, Seoul, Korea2nd International Symposium on Bio- and Nano-Electronics in Sendai, Dec. 9-10, 2006
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Todays TalkIntroduction to computational simulationRole of atomic scale simulation in nano-materials and devices researchCase Study : Asymmetry in atomic scale intermixing during deposition of thin metallic multilayers
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What is Computational Simulation?Research method to investigate a complex system based on the reasonable principles of a simple system. 10keV Ar on Au75eV C on diamond
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Molecular Dynamics Simulation
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Hierarchy of Computer Simulation
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Computation & Simulation in Atomic ScaleAb initio CalculationMolecular Dynamic Simulation
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Nanomaterials
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Characteristics of NanotechnologyContinuum media hypothesis is not allowed.
Band Theory
Diffusion and Mechanics
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Size Dependent Properties
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Scale Down Issues1~2nmKinetics based on continuum media hypothesis is not sufficient.
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Chracteristics of NanotechnologyContinuum media hypothesis is not allowed.
Large fraction of the atom lies at the surface or interface.Abnormal WettingAbnormal Melting of Nano ParticlesChemical Instabilities
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GMR Spin ValveMajor materials issue is the interfacial structure in atomic scale
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Nanoscience or Nanotechnologyneeds atomic scale understandings of structure, kinetics and properties.
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Insufficient Experimental Tools
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Methodology of Conventional R&D
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Methodology of Nanotechnology
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Computation & Simulation in Atomic ScaleAb initio CalculationMolecular Dynamic Simulation1nm = 1,000 atoms10nm= 1,000,000 atoms100nm=1,000,000,000 atoms
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Cluster Supercomputer & VisualizationBeowulf Cluster @ CALTECH
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Devices with Thin MultilayersMajor materials issue is the interfacial structure in atomic scale1~2nmGMR Spin Valve
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Thin Film Growth Model (conventional)
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Adatom (normal incident 0.1 eV)Co-Al EAM potential*x,y-axis : Periodic Boundary Conditionz-axis : Open SurfaceDeposition rate: 1.306 10-1 nm/nsecMD calc. step : 0.1fs300K Initial Temperature300K Constant TemperatureFixed Atom PositionCalculation MethodsR. 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).
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Deposition in Co-Al SystemCo on Al (001)Al on Co (001)
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Asymmetry in Interfacial Intermixing
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Radial Distribution Function of Interface CoAl compound layer of B2 structure was formed spontaneously.
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Al on Co(111)/(0001)Co on Al(111)Atomic deposition behavior
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Asymmetry in Interfacial Intermixing Deposition at 300K Initial kinetic energy 0.1eV
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Activation Barrier for IntermixingReaction Coordinate
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Adatom (normal incident 0.1 eV)Co-Al EAM potential*x,y-axis : Periodic Boundary Conditionz-axis : Open SurfaceDeposition rate: 1.306 10-1 nm/nsecMD calc. step : 0.1fs300K Initial Temperature300K Constant TemperatureFixed Atom PositionCalculation MethodsR. 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).
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Acceleration of Adatoms near Surface
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Kinetic Criteria for IntermixingLocal Acceleration3.5eV(1)(2)(3)(4)Activation Barrier for MixingReaction Coordinate
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Deposition in Co-Al SystemCo on Al (001)Al on Co (001)
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New Chinese Proverb?
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Asymmetry of Surface ReactionDo you have experimental evidence?
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FCC - AlMagnetic Properties of Co-Al systemSpin resolved DOS
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Magnetic properties of Co-Al Thin LayerSi substrateSi substrateSi substrateCu buffer layer (1500)Cu buffer layer (1500)Co (30)Co (30)Co (30)Al (30)Al (840)Cu Capping layer (50)Cu Capping layer (50)Cu Capping layer (50)MOKE(Magneto-Optic Kerr effects)
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Effect of Coating SequenceAlSi substrateCu buffer layer (1500)Co (30)Capping layer (50)
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Co Thickness Effect
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Effect of Coating SequenceAlSi substrateCu buffer layer (1500)Co (30)Capping layer (50)
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How thick is the nonmagnetic (B2) interlayer?
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Thickness of B2 Layer : 3ML3ML ~ 10
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SummaryAl on CoCo on AlAsymmetry in interfacial intermixing was observed in both MD simulation and experiment.
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AcknowledgementFinancial SupportCore Capability Enhancement Program of KIST (V00910, E19190)
CollaboratorsKISTMr. Sang-Pil KimDr. Seung-Cheol LeeHanyang UniversityProf. Yong-Jae Chung Yonsei UniversityProf. Chungnam Whang Dr. Jae Young ParkMs. Hyunmi Hwang
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Computational Materials Simulation Lab.http://diamond.kist.re.kr/SMS