1 Department of Materials Science

1
1 Department of Materials Science
Engineering, Chungnam National University,
Daejeon 305-764 Korea2 Department of Physics,
Andong National University, Andong 760-749, Korea
FABRICATION AND MAGNETIC PROPERTIES OF
ELECTRODEPOSITED Co-NANOWIRE ARRAYS USING
SELF-ASSEMBLED DIBLOCK COPOLYMER TEMPLATES

• Abstract
• In recent, there is a considerable interest in
  the fabrication of the magnetic nanowire arrays
  due to potential applications in magnetic
  recording media, sensors. We produced template
  for nanowire arrays using diblock copolymers
  composed of polystyrene and polymethylmethacrylate
  , P(S-b-MMA), with volume fraction of PS of 0.7.
  The 1 solutions of P(S-b-MMA) in toluene were
  spin-coated onto gold-coated silicon wafer. The
  diblock copolymer films were annealed for 24
  hours at 200 oC under an applied electric field
  of 1 kV between aluminized Kapton film placed on
  the film and bottom gold electrode. The annealed
  diblock copolymer films observed by AFM showed
  that PMMA cylinders with about 10 nm-diameter are
  hexagonally packed by self-assembly in a PS
  matrix due to the nature of self-assemble. The
  nanoporous PS films, 1.1 Tera holes/in2, were
  obtained by removing the PMMA cylinders through
  deep ultraviolet exposure and rinsing with acetic
  acid.
• The Co-nanowire arrays were fabricated by
  electrodeposition into the nanoporous PS films in
  potentiostatic mode with three electrode
  configurations. The electrodeposition solutions
  were 50g/l of CoSo4, 80g/l of NaSo4 and 40g/l of
  H3BO3 . Hysteresis curves of Co-nanowire arrays
  measured by VSM, revealed the perpendicular
  magnetic anisotropy to substrate.

• Nanotemplate

We have fabricated the nanotemplate. 11.76
nm diameter 26.47 nm distance 1.1 Tera
holes/in2

• There is a considerable interest in the
  fabrication of the magnetic nanowire arrays and
  dots due to potential applications in ultra-high
  density magnetic recording media and sensors.
• Nanofabrication
• Lithography is central to the top-down
  fabrication
• Self-assembled nanostructures are powerful route
  to the bottom-up fabrication (Topical Review
  J.I. Martin et. al. JMMM, 256, 449, 2003)
• Electrodeposited Co-nanowire arrays using
  self-assembled diblock copolymer template
• T.P. Russell et. al. Science, 290, 2126, 2000.
• Terabit density, high aspect ratio
• Simple and low cost technique

PS-PMMA
Au

• Magnetic property of the Co-nanowire arrays

• VSM measurement

• Diblock copolymer
• Consists of two different polymer chains
• Self-assembly
• Various structures with composition after
  annealing

Co nanowire
Co film
H
H
H
Shape Anisotropy Crystalline Anisotropy

• Process
• Solution of diblock copolymer
• Polystyrene and Polymethylmethacrylate( PS-PMMA)
  with fPS0.71
• 1 solutions of PS-PMMA in toluene
• Spin coating
• Onto gold-coated silicon wafer
• 4000 rpm for 30 sec
• Annealing under electric field
• 1 kV
• 200 oC during 1day
• UV etching
• Deep ultraviolet exposure for 90min.
• Rinsing with acetic acid.
• ED Solution
• 50g/l CoSo4, 80g/l NaSo4 , 40g/l H3BO3
• ED Condition
• - 1.0 V vs SCE

• Fabrication System
• Spin coating System
• Spin coater
• Annealing system under high electric field
• Temperature control
• Heating block
• Vacuum chamber
• High voltage power supply (max. 2kV)
• UV etching system
• UV Lamp and stand
• Chamber
• Electrodeposition system
• Potentio state
• ED Cell
• 3 electrodes configuration

• Magnetic property of the Co-nanowire arrays

• Hc vs magnetization angle

Co-nanowire
Co-film
Co -nanowires are well grown perpendicular to
substrate
ED Cell

• We have fabricated the nanotemplate
• 11.76 nm diameter
• 26.47 nm distance
• 1.1 Tera holes/in2
• We have fabricated the Co-nanowire arrays
• Few hundred nm length
• Perpendicular magnetic anisotropy to substrate

• AFM images

UV Etching
Self-assembled PMMA in PS matrix
Pores in PS matrix