My encounter with nanotechnology

My Encounter with NANOTECHNOLOGY

Hardev Singh VIRKVisiting 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.

NANONANO

• “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

Billions of nanometersA two meter tall male istwo billion nanometers.

The pinhead sized dot is a million nm

Biological cells size isThousands of nm

DNA Molecules are about 2.5 nm in width

Hydrogen atom spans 0.1 nm2 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.

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, co-precipitation, 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 • Ion Track Technology [1] was developed at GSI, Ion Track Technology [1] was developed at GSI,

Darmstadt. Ion Track Filters (ITFs) or Track-Darmstadt. Ion Track Filters (ITFs) or Track-etched membranes became precursors to etched membranes became precursors to development of nanotechnology during 1990s. development of nanotechnology during 1990s. ITFs were prepared by bombardment of thin ITFs were prepared by bombardment of thin polymer foils using heavy ions. One of the first polymer foils using heavy ions. One of the first applications of ITFs was separation of cancer applications of ITFs was separation of cancer blood cells from normal blood by making use of blood cells from normal blood by making use of Nuclepore filters. Author’s group used heavy ion Nuclepore filters. Author’s group used heavy ion beam facility available at GSI UNILAC, Darmstadt beam facility available at GSI UNILAC, Darmstadt during 1980s for Ion Beam Modification of during 1980s for Ion Beam Modification of Materials and to prepare ITFs in our laboratory. Materials and to prepare ITFs in our laboratory.

• [1] R. Spohr: [1] R. Spohr: Ion Tracks and Microtechnology: Principles and Applications Ion Tracks and Microtechnology: Principles and Applications (Vieweg Publications, Weisbaden Germany, 1990(Vieweg Publications, Weisbaden Germany, 1990

Ion Tracks as Structuring Tools Ion Tracks as Structuring Tools

• Ion tracks are created when high-energetic heavy Ion tracks are created when high-energetic heavy ions with energy of about 1 MeV/nucleon (e.g. ions with energy of about 1 MeV/nucleon (e.g. 140 MeV Xe ions) pass through matter. The 140 MeV Xe ions) pass through matter. The extremely high local energy deposition along the extremely high local energy deposition along the path leads to a material transformation within a path leads to a material transformation within a narrow cylinder of about 10 nm width. Unlike in narrow cylinder of about 10 nm width. Unlike in the more conventional lithographic techniques the more conventional lithographic techniques based on ion or electron beam irradiation, a based on ion or electron beam irradiation, a single heavy ion suffices to transform the single heavy ion suffices to transform the material. material.

Latent Pb-Ion Tracks in MicaLatent Pb-Ion Tracks in Mica

Size of Etched ION TracksSize of Etched ION Tracks

Large Etched Ion TracksLarge Etched Ion Tracks

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

Anodization of aluminum Start with uniform layer of ~1m 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 Template Preparation

(T. Sands/ HEMI group http://www.mse.berkeley.edu/groups/Sands/HEMI/nanoTE.html)

Anodic alumina (Al2O3) Template

100nm

Si substrate

alumina template

(M. Sander)

Electrolytic CellElectrolytic Cell

Replica of Nanowires

Microtubule Fabrication

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 nano- electronics. During failure of our Experiments, exotic patterns ( nanoflowers, nanocrystals, nanobuds) were produced under nature’s self assembly.

Template Synthesis of Copper Template Synthesis of Copper NanowiresNanowires

The concept of electro-deposition of metals is The concept of electro-deposition of metals is an electrochemical process. The etched pores of ITFs The etched pores of ITFs used would act as a template. The electrolyte used used would act as a template. The electrolyte used here was CuSO4.5H2O acidic solution. The rate of here was CuSO4.5H2O acidic solution. The rate of deposition of metallic film depends upon: current deposition of metallic film depends upon: current density, inter-electrode distance, cell voltage, density, inter-electrode distance, cell voltage, electrolyte concentration, pH value and temperature electrolyte concentration, pH value and temperature etc. In our case, electrode distance was kept 0.5 cm etc. In our case, electrode distance was kept 0.5 cm and a current of 2mA was applied for 1 hour. The and a current of 2mA was applied for 1 hour. The developed microstructures were scanned under SEM developed microstructures were scanned under SEM for morphological and structural studies.for morphological and structural studies.

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

SEM Images of Cu Nanowires using SEM Images of Cu Nanowires using Electrodeposition TechniqueElectrodeposition Technique

Copper Nanowire Bundles in AAMCopper Nanowire Bundles in AAM

Cu Nanowires under Constant CurrentCu Nanowires under Constant Current

Capping Effect of Current VariationCapping Effect of Current Variation

A Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper Nanoflowers

Copper Nanoflowers grown in Polymer Template (100nm pores)

Copper Lillies grown due to over- Copper Lillies grown due to over- deposition of Copper in AAM deposition of Copper in AAM

Copper Marigold Flower

SEM micrograph of Nanocrystals of SEM micrograph of Nanocrystals of Polycrystalline CopperPolycrystalline Copper

XRD Spectrum of polycrystalline XRD Spectrum of polycrystalline Copper nanocrystalsCopper nanocrystals

Position [°2Theta] (Copper (Cu))

10 20 30 40 50 60 70

Counts

0

20000

40000

60000

36.6

37 [

°]

38.2

83 [

°]

43.4

61 [

°]

45.4

48 [

°]

48.9

20 [

°]

50.5

80 [

°]

54.3

04 [

°]54.9

56 [

°]

64.8

09 [

°]

74.2

99 [

°]

KK1

XRD spectrum of Cu nanowiresXRD spectrum of Cu nanowires

Position [°2Theta] (Copper (Cu))

30 40 50 60 70 80 90

Counts

0

400

1600

Cu polycrystalline

SEM Image of CdS NanowiresSEM Image of CdS Nanowires

HRTEM image showing CdS Nanowire HRTEM image showing CdS Nanowire & Heterojunctions & Heterojunctions

I-V plot of CdS Nanowire arrays I-V plot of CdS Nanowire arrays showing RTD characteristics showing RTD characteristics

SEM image of Cu-Se NanowiresSEM image of Cu-Se Nanowires

Cu-Se nanowires exhibit p-n junction Cu-Se nanowires exhibit p-n junction diode characteristicsdiode 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

• Ambipolar transport• Carrier mobility study• Quantum effect

A single device for numerous applications

Device physics study

Role of Nanowires for Next-Generation 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.

Reverse Miceller Route

Nanoparticle Synthesis (ME route)

TEM images of Barium Carbonate Nanorods

TEM images of Iron Oxalate and Barium Oxalate Nanocrystals

TEM image of CdO Quantum Dots

Conversion of Quantum Dots of CdO Conversion of Quantum Dots of CdO to Nanorods using EDA to Nanorods using EDA

CdS Nanocrystals(CTAB+n-butanol)

CdS Nanoneedles(CTAB+n-hexanol)

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

Thank You !!!