The Applications of Nano Materials

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The Applications of Nano Materials

• Department of Chemical and Materials Engineering
• San Jose State University

Zhen Guo, Ph. D.
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How to study Nanomaterials
Part I -- Done
Basic Materials Science Principles
Microstructure
Properties
Materials
Applications
Processing
Part III
Part II This one
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Nano Structure and Device

• Nano structure and device can be accomplished by
  two approaches.
• -- Bottom Up method where small building blocks
  are produced and assembled into larger
  structures.
• examples chemical synthesis, laser trapping,
  self assembly, colloidal aggregation, etc
• -- Top Down method where Large object are
  modified to give smaller features.
• examples film deposition and growth, nano
  imprint / lithography, etching technology,
  mechanical polishing

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Technology and Characterization of Nano Material
Science Session VI Nano Technology Bottom Up
Approach Session VII Nano Technology Top Down
Approach Session VIII Nano Material
Characterization
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Session VI Nano Materials Synthesis
Nano metallic particle synthesis Nano
semiconductor materials synthesis Carbon based
nano structure synthesis Self assembly nano
materials
Challenge The control of nano particle sizes,
distributions and their locations
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Nano Metallic Magnetic Particles

• Nano metallic particles include single metals
  mainly transition metals, alloyed metals and
  metal oxide nano particles
• The applications of metallic nano particles are
• -- High density magnetic data storage
• -- Dilute magnetic semiconductor (DMS)
• -- Biomedical applications (MRI, NMR, SQUID)
• -- Highly active catalyst (large surface area)
• -- Nucleus for CNT and other nano tube

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Synthesis of Single Metal MNP-- Method I The
Reduction of Metal Salts

• Size control conducting the reaction in a
  confined reactor
• Nano confined reactor such as water-in-oil or
  oil-in-water micro-emulsion system
• Size of confined space can be defined by varying
  amount of both surfactant and solvent
• Successful examples included Fe, Ni and Co
  particles

Courtesy from Vincent Rotello, Nanoparticles
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Synthesis of Single Metal MNP-- Method II
Thermal Decomposition

• Thermal Decomposition of organo-metallic
  complexes can produce highly mono-disperse nano
  particles.
• Size and dispersity control is attained through
  high reaction temperature
• Capping ligands (e.g. Oleic Acid) can also
  mediate the particle growth by forming a
  monolayer of nano particles
• Most common precursors Metal Carbonyl
  complexes.
• Morphology can also be controlled through
  various capping ligands

TOPO Trioctylphosphine Oxide
Courtesy from Vincent Rotello, Nanoparticles
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Alloyed Metal Nano Particles

• Solid-solution alloyed metallic nano particles
  can be attained through simultaneous thermal
  decomposition
• Core-shell alloyed nano particles are produced
  by a stepwise reduction process where each
  successive step uses larger diameter water
  droplet to yield the alloyed core-shell particles

Courtesy from Vincent Rotello, Nanoparticles
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Metal Oxide Nano Particles

• Thermal decomposition of metal organic
  precursors on a hot surface.
• The size of the nano particles can be controlled
  by reaction temperature and / or the ratios of
  precursor verse capping ligands

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Nano Silicon Particles
Cubic Si Nano crystals are made by PECVD method
of injecting a dilute mixture (5 SiH4 and 95 of
He) and applying RF power
Thermal Evaporation of Si chips and collected
nano particles in a cold chamberl
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Other Nano Silicon Particles

• Thermal Evaporation
• Sputtering
• Laser ablation
• Electrochemical Etching with catalyst
• Implant (Si, Ge)
• Anneal from Si-rich SiOx (self assembly)

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Semiconductor Compound Nano Particles

• High Temperature Organo-Metallic Methods are
  still the most popular for both III-V and II-VI
  compound.
• Thermal decomposition
• Rapid injection of organometallic precursor means
  fast nucleation.
• The following growth can be controlled and
  terminated by adjusting temperature

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Carbon based nano structures
Bucky ball
Carbon nano tube
http//www.nccr-nano.org/nccr/media/gallery/galler
y_01/gallery_01_03
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Why Ball and Tube Shape?

• In Nano Material Science, high surface and even
  edge energy matters.
• As we previously discussed, a tiny piece of
  graphite would have a lot of atoms at its edge
  which is unstable.
• Giving opportunities, nano solids would roll
  them self up to bucky balls or tubes to minimize
  the total energy

http//nanonet.rice.edu/intronanosci/sld005.html
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Making Buckminsterfullerene

• Carbon Arc Experiments
• -- Two Carbon robs arcing in He at 100 Torr.
• -- Can now be reproduced in gram level at a time
• First discovered in 1985, it is most known nano
  particles
• The round cage like structure of the fullerenes
  was reminiscent of the dome structures designed
  by the architect Richard Buckminster Fuller, and
  so it was named Buckminsterfullerene

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Mechanisms of Carbon Nano tube

• Root Growth Mechanism
• Transition metal as catalyst
• Hydrocarbon dissociate at metal surface into H
  and C.
• Once surface saturated with C, it starts to form
  as graphite sheet with fullerene cap
• More C atoms can be inserted into Metal-C bond
  so the tube get growing longer.

Courtesy from Rainer Waser Nano-electronics and
Information technology
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Synthesis Methods for CNT

• Electric Arc Discharge similar with the one for
  Bucky Ball
• Laser Vaporization Graphite target with Co, Ni
  powders sitting in 1200C furnace and hit by laser
  pulse. CNT collected downstream at cold finger.
• CVD pre-patterned structure with Fe, Mo nano
  particles in a tube furnace at 1000C and methane
  as precursor of carbon
• Fullerene recrystallization depositing Ni and
  C60 multi-layers and recrystallize at 900C

Courtesy from Rainer Waser Nanoelectronics and
Information technology
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Properties of Carbon Nano Tube

• There are different ways to roll up the graphite
  sheet to form carbon nano tube. This
  configuration is defined as Chirality
• The electronic properties of carbon nano tube are
  determined by its chirality.
• It can be semiconductor, semimetals or metals

Courtesy from Stanley Wolfe Advanced Silicon
Processing
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Self Assembly of Carbon Nano Tube as interconnect
(Metal)
Courtesy from Stanley Wolfe Advanced Silicon
Processing
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Canbon Nano Tube Semiconductor
Single or Multiple Carbon Nano Tube as FET Channel
Courtesy from Stanley Wolfe Advanced Silicon
Processing
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Self Assembly Nano Technology

• Self assembly can be defined as a coordinated
  actions of independent entities under local
  control of driving forces to produce a large,
  ordered structures or to achieve a desired group
  effect.
• The driving force of self assembly is usually
  based on an interplay of thermodynamics and
  kinetics.
• -- Chemically Controlled Self-assembly
• -- Physically Controlled Self-assembly
• -- Flip-up Principles and Spacer Techniques

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Chemically Controlled Self Assembly
Deposition of loaded diblock copolymer micelles

• One block is soluble in toluene and the other is
  insoluble.
• Spherical micelles of copolymer molecular are
  formed in toluene
• These micelles are loaded with compounds such as
  HAuCl4 and deposited on planar substrate.
• Oxygen plasma treatment pyrolyses the polymer
  and turn precursor into nano Au particles with
  short range regular pattern

Courtesy from Rainer Waser Nano-electronics and
Information technology
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Hybrid approach for self assembly

• A template with holes is created using typical
  lithography
• The deposition process of the micelles is
  controlled that only those micelles into grooves
  and holes by caterpillar force will remain on the
  surface after resist removal.
• Copolymer is pyrolysed and a regular Au dot
  array obtained

Courtesy from Rainer Waser Nano-electronics and
Information technology
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Why Nano Gold Particles?
The optical applications of nano materials
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Hybrid Approach (II)

• A diblock copolymer solution were spin-coated
  and annealed to promote phase separation into
  nano scale polymer domains. (Polystyrene and
  PMMA)
• One phase is removed with an organic solvent,
  leaving a porous PS films.
• This highly ordered porous film serve as
  hardmask to etch into Oxide.
• Conformally deposit aSi and etch them using an
  anisotropic RIE process.
• Annealing to form Si Nano crystal array as
  floating gate

Courtesy from K. W. Guarini et al, IEDM 2003
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Physically Controlled Self Assembly

• Film deposition method using Stranski Krastanov
  Growth. Followed by initial layer by layer
  growth, island-like nano dots are formed to
  reduce the elastic strain energy (see next
  session)
• This technique can also combined with
  Lithography. Layer 2 can be conventionally
  patterned. Then alternative Layer 1 and 2 deposit
  can lead to a perfect SiGe islands at specific
  location.

Courtesy from Rainer Waser Nano-electronics and
Information technology
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Flip-up principle and Spacer technique

• Flip-up principle utilized the accurate control
  of film thickness at nm scale during deposition
  and flip it to vertical dimension
• The most known method is spacer technique where
  a hard mask is deposited conformally over a
  coarse structure.
• Then the film were etched anisotropically
  leaving only spacer to define nano feature
• The next patterning used the spacer as hard mask
  and thus turn nano-scale controlled film
  thickness into vertical fine structure

Courtesy from Rainer Waser Nano-electronics and
Information technology