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The Applications of Nano Materials

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Title: The Applications of Nano Materials


1
The Applications of Nano Materials
  • Department of Chemical and Materials Engineering
  • San Jose State University

Zhen Guo, Ph. D.
2
How to study Nanomaterials
Part I -- Done
Basic Materials Science Principles
Microstructure
Properties
Materials
Applications
Processing
Part III
Part II This one
3
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

4
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
5
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
6
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

7
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
8
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
9
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
10
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

11
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
12
Other Nano Silicon Particles
  • Thermal Evaporation
  • Sputtering
  • Laser ablation
  • Electrochemical Etching with catalyst
  • Implant (Si, Ge)
  • Anneal from Si-rich SiOx (self assembly)

13
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

14
Carbon based nano structures
Bucky ball
Carbon nano tube
http//www.nccr-nano.org/nccr/media/gallery/galler
y_01/gallery_01_03
15
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
16
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

17
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
18
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
19
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
20
Self Assembly of Carbon Nano Tube as interconnect
(Metal)
Courtesy from Stanley Wolfe Advanced Silicon
Processing
21
Canbon Nano Tube Semiconductor
Single or Multiple Carbon Nano Tube as FET Channel
Courtesy from Stanley Wolfe Advanced Silicon
Processing
22
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

23
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
24
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
25
Why Nano Gold Particles?
The optical applications of nano materials
26
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
27
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
28
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
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