Atomic Scale Understanding of Intermixing Behavior of Thin Metal Multlayer

1
Atomic Scale Understanding of Intermixing
Behavior of Thin Metal Multlayer

• Sang-Pil Kim, Jae-Young Park, Seung-Cheol Lee,
• Yong-Jae Chung, Chung-Nam Whang and Kwang-Ryeol
  Lee
• Korea Institute of Science and Technology, Seoul,
  Korea
• Hanyang University, Seoul, Korea
• Yonsei University, Seoul, Korea

2
Devices with Thin Multilayers
12nm
GMR Spin Valve
Major materials issue is the interfacial
structure in atomic scale
3
Thin Film Growth Model (conventional)
4
Calculation Methods
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
• Deposition rate 1.306 10-1 nm/nsec
• MD calc. step 0.1fs

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).
5
Deposition in Co-Al System
Co on Al (001)
Al on Co (001)
6
Asymmetry in Interfacial Intermixing
7
Radial Distribution Function of Interface

• CoAl compound layer of B2 structure was formed
  spontaneously.

8
Atomic deposition behavior
Co on Al(111)
Al on Co(111)/(0001)
9
Asymmetry in Interfacial Intermixing

• Deposition at 300K
• Initial kinetic energy 0.1eV

10
Asymmetry in Au-Pt
Au on Pt (001)
Pt on Au (001)
11
Deposited Atom of 5.0 eV
Co on Cu (100)
Cu on Co (100)
12
Ion Scattering Spectroscopy

• CoAxial Impact Collision Ion Scattering
  Spectroscopy (CAICISS)
• Energy range of keV ? penetration depth lt
  10 Å

13
Polar Scan in 1100 on Co (0001) Surface

14
Polar scan of Al added Co (0001)
DFT calculation results
15
Al on Co (0001) Surface
16
Polar Scan in 100 on Al (001) Surface
A121 (31.7)
A121 (58.3)
A132 (32.7)
A11 (12.9)
A122 (26.4)
A122 (11.52)
A132 (20.4)
A130 (79.1)
17
Polar Scan of Co added Al (001)
18
Magnetic Properties of Co-Al system
FCC - Al
Spin resolved DOS
19
Magnetic properties of Co-Al Thin Layer
MOKE (Magneto-Optic Kerr effects)
Capping layer (50Å)
Capping layer (50Å)
Capping layer (50Å)
Co (30Å)
Co (30Å)
Al (30Å)
Co (30Å)
Cu buffer layer (1500Å)
Al (840Å)
Cu buffer layer (1500Å)
Si substrate
Si substrate
Si substrate
20
Co Thickness Effect
21
Effect of Coating Sequence
Capping layer (50Å)
Co (30Å)
Cu buffer layer (1500Å)
Si substrate
Al
22
How thick is the nonmagnetic (B2) interlayer?
5Å
7Å
30Å
10Å
23
Thickness of B2 Layer 3ML
3ML 10Å
24
Summary
Co on Al
Al on Co
Asymmetry in interfacial intermixing was observed
in both MD simulation and experiment.
25
A Novel Process
26
Acknowledgement

• Financial support from
• Core Capability Enhancement Program of KIST

27
Asymmetry in Interfacial Intermixing

• Deposition at 300K
• Initial kinetic energy 0.1eV

28
Kinetic Criteria for Intermixing
Activation Barrier for Mixing
Reaction Coordinate
29
Kinetic Criteria for Intermixing
Local Acceleration
Activation Barrier for Mixing
(1)
3.5eV
(2)
(3)
(4)
Reaction Coordinate
30
(No Transcript)
31
Deposition in Co-Al System
Co on Al
Al on Co
32
Kinetic Criteria for Intermixing
Local Acceleration
Activation Barrier for Mixing
(1)
3.5eV
(2)
(3)
(4)
Reaction Coordinate
33
Asymmetry
34
Molecular Dynamic Simulation
Interatomic Potentials

• Empirical Approach
• First Principle Approach