My encounter with nanotechnology

My Encounter with
NANOTECHNOLOGY
Hardev Singh VIRK
Visiting Professor
Sri Guru Granth Sahib World
University, Fatehgarh Sahib (Pb.)India

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.

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.

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.

• AFM Imaging of ATOMS of GOLD (Au 111)

Atomic Lattice Structure of HOPG in 3D
Topography using Atomic Force Microscope

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

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).

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.

My encounter with nanotechnology

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.

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.

UNILAC at GSI Darmstadt (Germany)

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

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.

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

Polymer Template Synthesis of
Nanowires

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

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)

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.

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.

AFM image of hexagonal pores of
Anodic Alumina Membrane (AAM)

SEM Images of Cu Nanowires using
Electrodeposition Technique

Copper Nanowire Bundles in AAM

Cu Nanowires under Constant Current

Capping Effect of Current Variation

A Garden of Copper Nanoflowers

Copper Nanoflowers grown in Polymer
Template (100nm pores)

Copper Lillies grown due to overdeposition of Copper in AAM

SEM micrograph of Nanocrystals of
Polycrystalline Copper

10
20
30
40
50

Position [°2Theta] (Copper (Cu))
60
7 4.29 9 [ °]

6 4.80 9 [ ° ]

KK1
5 0.58 0 [ ° ]

Counts

54 .3 04 [ ° ]
5 4.95 6 [ ° ]

48 .9 20 [ ° ]

45 .448 [ ° ]

43 .4 61 [ ° ]

38.2 83 [ °]

3 6.63 7 [ ° ]

XRD Spectrum of polycrystalline
Copper nanocrystals
60000

40000

20000

0
70

XRD spectrum of Cu nanowires
Counts
Cu polycrystalline

1600

400

0
30

40

50

60

70

Position [°2Theta] (Copper (Cu))

80

90

HRTEM image showing CdS Nanowire
& Heterojunctions

I-V plot of CdS Nanowire arrays
showing RTD characteristics

Cu-Se nanowires exhibit p-n junction
diode characteristics

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

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)

Nanowire Field-Effect Transistor
A single device for numerous applications
Device physics study
• Ambipolar transport
• Carrier mobility study
• Quantum effect

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.

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.

Nanoparticle Synthesis (ME route)

TEM images of Barium Carbonate
Nanorods

TEM images of Iron Oxalate and
Barium Oxalate Nanocrystals

Conversion of Quantum Dots of CdO
to Nanorods using EDA

CdS Nanocrystals(CTAB+n-butanol)

CdS Nanoneedles(CTAB+nhexanol)

Ba-M Hexaferrite Crystals (ME)

Ba-M Hexaferrite Crystals (CP)

Ba-hexaferrite ME(after
calcination)

Ba-hexaferrite CP(after calcination)

Hysteresis loops of Ba-hexaferrite
nanoparticles (CP & ME samples)

SEM image of ZnO Nanocrystals in
Ethanol and Nanorod(adding EDA)

TEM image of Ag quantum dots and
embedded nano particles

My encounter with nanotechnology

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