This Presentation is based on our Research work carried out in GNDU Amritsar and DAVIET, Jallandhar. We fabricated Ion track filters; nanowires and some Exotic Patterns for the first time in India using simple Techniques.
2. Birth of Nanotechnology
“There's Plenty of Room at the Bottom”
• On December 29, 1959, Richard P. Feynman
gave the seminal talk at a meeting at Caltech
of the American Physical Society. He
presented a vision of the precise manipulation
of atoms and molecules so as to achieve
amazing advances in information technology,
mechanical devices, medical devices, and
other areas.
3. Changing Idea into Reality
Eric Drexler of MIT, the Chemist, established
the modern field of nanotechnology, with a
draft of his seminal Ph.D. thesis in the mid
1980s. His 1991 doctoral thesis at MIT was
revised and published as the book
"Nanosystems,
Molecular
Machinery
Manufacturing and Computation" (1992),
which received the Association of American
Publishers award for Best Computer Science
Book of 1992.
4. NANO
•
“NANO” means “DWARF” in Greek.
•
Mathematically nano is ten to the power of minus nine …….. Make sense?
•
If the size of your shoe was one nano meter, then a meter would be the
distance that you would cover round the world and the sun and back.
•
One hydrogen atom is 0.1nm. Five atoms of carbon would occupy a space of
about 1 nm wide.
•
The nano world comes just after the femto world (10-15 m) of NUCEI and pico
world (10-12m) of atoms.
•
The nano marks the boundary between the classical and quantum mechanical
worlds
•
Most of the bulk substances behave differently from nanosize particles. A coin
of gold is golden yellow in color, but nanoscale gold is red; bulk gold is inert,
but nanogold can be a catalyst for chemical reactions.
7. The Incredible Tininess of Nano
The pinhead
sized dot is a
million nm
Billions of nanometers
A two meter tall male is
two billion nanometers.
DNA Molecules
are about 2.5
nm in width
Biological
cells size is
Thousands
of nm
Hydrogen atom
spans 0.1 nm
2 Uranium
atoms span 1 nm
8. Why Study Nanomaterials?
• Nanostructures (< 30 nm) have become an
exciting research field.
• – New physics phenomena affect physical
properties.
• – Unusual quantum effects and structural
properties.
• – Promising applications in optics, electronics,
thermoelectric, magnetic storage, NEMS
(nano-electro-mechanical systems).
9. Quantum Confinement Effects
– Quantum dots (0-D): confined states, and no
freely moving ones
– Nanowires (1-D): particles travel only along the
wire direction
– Quantum wells (2-D): confines particles within a
thin layer
There is no confinement
effect in Bulk materials.
Refer to energy distribution.
10.
11.
12. Routes to Nanotechnology
• Physical, chemical, biological and nature’s self
assembly.
• Top-down and bottom-up approaches.
• Chemical route to nanotechnology is simpler,
cheaper and allows fabrication at bench top
conditions.
• Reverse micelles (microemulsions route) is a
versatile method to produce a variety of
nanoparticles.
13. My Route to Nanotechnology
• Ion Track Technology Route using Heavy Ion
Beams from GSI, Darmstadt & JINR, Dubna.
• Chemical Route of Reverse micelles, coprecipitation, solvo-thermal, sol-gel and seed
growth techniques.
• Quantum dots, nanorods and nanoneedles of
Barium Carbonate, Barium Oxalate, Iron Oxalate,
Barium hexaferrite, Zinc Oxide, Cadmium
Sulphide, Cadmium Oxide and Silver prepared.
15. Ion Track Technology
• Ion Track Technology [1] was developed at GSI,
Darmstadt. Ion Track Filters (ITFs) or Tracketched membranes became precursors to
development of nanotechnology during 1990s.
ITFs were prepared by bombardment of thin
polymer foils using heavy ions. One of the first
applications of ITFs was separation of cancer
blood cells from normal blood by making use of
Nuclepore filters. Author’s group used heavy ion
beam facility available at GSI UNILAC, Darmstadt
during 1980s for Ion Beam Modification of
Materials and to prepare ITFs in our laboratory.
•
[1] R. Spohr: Ion Tracks and Microtechnology: Principles and Applications
(Vieweg Publications, Weisbaden Germany, 1990
16.
17. Ion Tracks as Structuring Tools
• Ion tracks are created when high-energetic heavy
ions with energy of about 1 MeV/nucleon (e.g.
140 MeV Xe ions) pass through matter. The
extremely high local energy deposition along the
path leads to a material transformation within a
narrow cylinder of about 10 nm width. Unlike in
the more conventional lithographic techniques
based on ion or electron beam irradiation, a
single heavy ion suffices to transform the
material.
21. Nanowire Fabrication
Template synthesis using polymer and anodic
alumina membranes
Electrochemical deposition
Ensures fabrication of electrically continuous wires
since only takes place on conductive surfaces
Applicable to a wide range of materials
High pressure injection
Limited to elements and heterogeneously-melting
compounds with low melting points
Does not ensure continuous wires
Does not work well for diameters < 30-40 nm
Chemical Vapor Deposition (CVD) or VLS technique
Laser assisted techniques
23. Anodic Alumina Template Preparation
Anodization of aluminum
Start with uniform layer of ~1µm Al
Al serves as the anode, Pt may serve as the cathode, and
0.3M oxalic acid is the electrolytic solution
Low temperature process (2-50C)
40V is applied
Anodization time is a function of sample size and distance
between anode and cathode
Key Attributes of the process (per M. Sander)
Pore ordering increases with template thickness – pores are
more ordered on bottom of template
Process always results in nearly uniform diameter pore, but not
always ordered pore arrangement
Aspect ratios are reduced when process is performed when in
contact with substrate
24. Anodic alumina (Al2O3) Template
(T. Sands/ HEMI group http://www.mse.berkeley.edu/groups/Sands/HEMI/nanoTE.html)
alumina template
Si substrate
100n
m
(M. Sander)
28. Electrochemical Synthesis
• Electrochemistry has been used to fabricate
nanowires and heterojunctions of Cu, Cu-Se
and Cd-S. The results of our investigations can
be exploited for fabrication of nanodevices for
application in opto-electronics and nanoelectronics. During failure of our Experiments,
exotic patterns ( nanoflowers, nanocrystals,
nanobuds) were produced under nature’s self
assembly.
29. Template Synthesis of Copper
Nanowires
The concept of electro-deposition of metals is an
electrochemical process. The etched pores of ITFs
used would act as a template. The electrolyte used
here was CuSO4.5H2O acidic solution. The rate of
deposition of metallic film depends upon: current
density, inter-electrode distance, cell voltage,
electrolyte concentration, pH value and temperature
etc. In our case, electrode distance was kept 0.5 cm
and a current of 2mA was applied for 1 hour. The
developed microstructures were scanned under SEM
for morphological and structural studies.
30. AFM image of hexagonal pores of
Anodic Alumina Membrane (AAM)
31. SEM Images of Cu Nanowires using
Electrodeposition Technique
47. A Billion Dollar Question …
• What can nanowires offer for semiconductor
nanoelectronics?
• Nonlithographic & extremely cost-effective
• Reduced phonon scattering: High carrier
mobility but reduced thermal conductance(?)
• Tunable electrical/optical properties
• Large surface-to-volume ratio: Sensor
sensitivity & memory programming efficiency
48. Advantages of 1-D Nanowires
• High-quality single-crystal wires with nearly
perfect surface
• Scalable nanostructure with precisely
controlled critical dimensions
• Best cross-section for surround-gate CMOS
• Very cost-effective materials synthesis
• High transport low-dimensionality structure
• May use as both device and interconnect for
ultra-compact logic (e.g., SRAM)
49. Nanowire Field-Effect Transistor
A single device for numerous applications
Device physics study
• Ambipolar transport
• Carrier mobility study
• Quantum effect
50. Role of Nanowires for NextGeneration Electronics
• The chemical and physical characteristics of
nanowires, including composition, size,
electronic and optical properties, can be
rationally controlled during synthesis in a
predictable manner, thus making these
materials attractive building blocks for
assembling electronic and optoelectronics
nanosystems.
51. Some Observations & Remarks
• Nanotechnology will be the driving force for
next technology revolution.
• Nanowires open door to a wonderland where
the next generation electronics would emerge.
• Scope for innovating new synthesis method
and complex functional nanostructures.
• New device and interconnect concepts will
emerge from horizon, driven by materials
synthesis.