EMA 5015Introduction to Nanomaterials

Dr. Chunlei (Peggy) WangMechanical and Materials Engineering

Florida International University

Outline

� History/motivation� What is a nanometer?� Controlling matter at the nanoscale� Properties� Applications� Educational issues

“640K ought to be enough for anybody”- Bill Gates, 1981

There’s Plenty of Room at the Bottom:An Invitation to Enter a New Field of Physics

“People tell me about miniaturization, and how far it has progressed today. They tell me about electric motors that are the size of the nail on your small finger. And there is a device on the market, they tell me, by which you can write the Lord's Prayer on the head of a pin. But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction. Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin?”

Richard Feynman

Cal Tech, 1959

Historical Use of Nanoparticles:Stained Glass

The Lycurgus Cup, dating from the 4th century A.D., is made from glass impregnated with gold nanoparticles; seen in (a) transmitted light and (b) reflected light.

What is really new about nanotechnology?

Nanosized particles of Ag, Au, and Cu

� This technology is not new, it is the combination of existing technologies and our new found ability to observe and manipulate at the atomic scale, this makes nanotechnology so compelling from scientific, business and political viewpoints.

What is really new about nanotechnology?

Milestones

: 1857, Michael Faraday discovers colloid gold.

: 1905, Albert Einstein explains the existence of colloids.

: 1932, Langmuir discovers layers of atoms one molecule thick: Langmuir established the existence of monolayers (layers of atoms or molecules one atom thick). These monolayers have peculiar two dimensional qualities, and led to the development of a totally transparent glass produced by forming a thin film of fluorine compound on the surface.

: 1958, Feynman suggests that there is ‘plenty of room’ to work at the nanoscale– this was the first vision of the possibilities of science and technology at the nanoscale.

: 1974, The word ‘nanotechnology’ first used: The term ‘nanotechnology’ was coined in 1974 by Norio Taniguchi of the University of Tokyo. (‘On the Basic Concept of “NanoTechnology”’, Proceedings of the International Conference of Production Engineering, 1974)

: 1981, Gerd Binning and Heinrich Rohrer invented the Scanning Tunneling Microscope (STM) at IBM.

: 1985, Richard Smalley, Robert Curl and Harold Kroto discovered C60 while investigating the outer atmosphere of stars, for whichthey were awarded the Nobel Prize in 1996.

Milestones 35 xenon atoms on a nickel (110) surface

Milestones

: 1991, Sumino Iijima discovered a process to make ‘graphitic carbon needles ranging from 4nm to 30nm in diameter and 1 micron in length’ (Nature 354, 1991, 56). In 1993 the first single-walled nanotubes (SWNT) were produced.

: 1998 (unofficially since 1996), National Nanotechnology Initiatives (NNI) founded under National Science and Technology Council. http://www.nano.gov/

: • US government spending on nanotechnology grew to $6.4 billion in 2006, up 10% from $5.9 million in 2005. The U.S. leads on this metric, with $1.78 billion from federal and state governments, followed by Japan with $975 million and Germany with $563 million. • Corporations spent $5.3 billion on nanotech R&D in 2006.

Invention of the Transistor

Bell Laboratories, 1947

John BardeenWalter BrattainWilliam Shockley

� There are many different types of transistors, but the basic theory of their operation is all the same. The three elements of the two-junction transistor are (1) the EMITTER, which gives off, or emits," current carriers (electrons or holes); (2) the BASE, which controls the flow of current carriers; and (3) the COLLECTOR, which collects the current carriers.

� The arrow always points in the direction of hole flow, or from the P to N sections, no matter whether the P section is the emitter or base. On the other hand, electron flow is always toward or against the arrow, just like in the junction diode.

Definitions of ICs

� A forward biased PN junction is comparable to a low-resistance circuit element because it passes a high current for a given voltage. In turn, a reverse-biased PN junction is comparable to a high-resistance circuit element. By using the Ohm's law formula for power (P = I2R) and assuming current is held constant, you can conclude that the power developed across a high resistance is greater than that developed across a low resistance. Thus, if a crystal were to contain two PN junctions (one forward-biased and the other reverse-biased), a low-power signal could be injected into the forward-biased junction and produce a high-power signal at the reverse-biased junction. In this manner, a power gain would be obtained across the crystal. This concept is the basic theory behind how the transistor amplifies.

Definitions of ICs

IC

“No Exponential is Forever … but We Can Delay ‘Forever’,”Gordon E. Moore, International Solid State Circuits Conference, Feb. 10, 2003.

� The term transistor is derived from the words TRANSfer and resISTOR. This term was adopted because it best describes the operation of the transistor - the transfer of an input signal current from a low-resistance circuit to a high-resistance circuit. Basically, the transistor is a solid-state device that amplifies by controlling the flow of current carriers through its semiconductor materials.

� An advanced microprocessor, as of 2006, can use as many as 1.7 billion transistors (MOSFETs)

� Types of transistors:� Bipolar Junction Transistor (BJT)� The Field-Effect Transistor (FET)� MOS transistor [see Metal Oxide Semiconductor (MOS) Capacitor]

Complementary metal–oxide–semiconductor (CMOS)

Definitions of ICs

� A chip or an integrated circuit (IC) is a small electronic device made out of a semiconductor material. The integrated circuit consists of elements inseparably associated and formed on or within a single SUBSTRATE (mounting surface). In other words, the circuit components and all interconnections are formed as a unit. The first integrated circuit was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor. Integrated circuits are used for a variety of devices, including microprocessors, audio and video equipment, and automobiles. Integrated circuits are often classified by the number of transistors and other electronic components they contain:

* SSI (small-scale integration): Up to 100 electronic components per chip (1960s)

* MSI (medium-scale integration): From 100 to 3,000 electronic components per chip

* LSI (large-scale integration): From 3,000 to 100,000 electronic components per chip

* VLSI (very large-scale integration): From 100,000 to 1,000,000 electronic components per chip (1980s)

* ULSI (ultra large-scale integration): More than 1 million electronic components per chip

Definitions of ICs

First IC, September 12, 1958

Moore’s Law

“Cramming More Components Onto Integrated Circuits”Author: Gordon E. MoorePublication: Electronics, April 19, 1965

IC

Molecular Nanoelectronics?

� Projected timeline for the electronics industry:

A. C. Seabaugh, P. Mazumder,Proceedings of the IEEE, 87, 535 (1999).

“Soon researchers will bring us devices that can translate foreign languages as fast as you can talk; materials 10 times stronger than steel at a fraction of the weight;and -- this is unbelievable to me -- molecular computers the size of a tear drop with the power of today's fastest supercomputers.”-President William J. Clinton, January 27, 2000

What is a Nanometer?

Assume that a cubic-shaped transistor in a computer chip has volume of 10nm3. How many would fit into a 5-mL drip of water? If currently one billion transistors are fabricated every second, how much time in years is required to manufacture this number of transistors?

5x1020

16,000!

What is a Nanometer?

� Consider a human hand:

What is a Nanometer?

What is a Nanometer?

What is a Nanometer?

Nanofabrication

Top-Down: Photolithography

Top-Down: Nanoimprint Lithography

Top-Down: Nanosphere Lithography

Bottom-Up: Molecular Self-Assembly

Microcontact Printing

Dip Pen Nanolithography

Nanolithography with Ultra-high VacuumScanning Tunneling Microscopy

Bottom-Up: Carbon Nanotube Synthesis

Top-Down and Bottom-Up

� Top-down: Imperfection of the surface structure� Have a reduced conductivity due to inelastic surface scattering

� Generation of excessive heat and thus impose extra challenges to the device design and fabrication

� Introduction of internal stress

� Bottom-up: � Less defects, more homogeneous chemical composition, better

short and long range ordering

� Driven mainly by the reduction of Gibbs free energy, so that nanomaterials such produced are in a state closer to a thermodynamic equilibrium state

Red blood cells(~7-8 µm)

Things NaturalThings Natural Things ManmadeThings Manmade

Fly ash~ 10-20 µm

Head of a pin1-2 mm

Quantum corral of 48 iron atoms on copper surfacepositioned one at a time with an STM tip

Corral diameter 14 nm

Human hair~ 60-120 µm wide

Ant~ 5 mm

Dust mite

200 µm

ATP synthase

~10 nm diameterNanotube electrode

Carbon nanotube~1.3 nm diameter

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The Challenge

Fabricate and combine nanoscale building blocks to make useful devices, e.g., a photosynthetic reaction center with integral semiconductor storage.

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0.1 nm

1 nanometer (nm)

0.01 µµµµm

10 nm

0.1 µµµµm100 nm

1 micrometer (µµµµm)

0.01 mm

10 µµµµm

0.1 mm100 µµµµm

1 millimeter (mm)

1 cm

10 mm10-2 m

10-3 m

10-4 m

10-5 m

10-6 m

10-7 m

10-8 m

10-9 m

10-10 m

Visible

Nan

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1,000 nanometers = Infrared

Ultraviolet

Microwave

Soft x-ray

1,000,000 nanometers =

Zone plate x-ray “lens”Outer ring spacing ~35 nm

Office of Basic Energy SciencesOffice of Science, U.S. DOE

Version 05-26-06, pmd

The Scale of Things The Scale of Things –– Nanometers and MoreNanometers and More

MicroElectroMechanical(MEMS) devices10 -100 µm wide

Red blood cellsPollen grain

Carbon buckyball~1 nm diameter

Self-assembled,

Nature-inspired structure

Many 10s of nm

Atoms of siliconspacing 0.078 nm

DNA~2-1/2 nm diameter

Importance of Surface

� Everything has Surface or interface

� Surface science: a discipline that is devoted to the investigation of two-dimensional structures.

� Surface perform numerous vital functions:

� They keep things in; they keep things out; or they allow the flow of material and energy across an interfacial structure.

� Catalysts: Surfaces are capable of initiating or terminating chemical reactions

Nature is the ultimate nanotechologist, at the nano-, the micro- and the macroscales!

Natural Perspective

� Organisms has developed numerous means of increasing surface area to meet metabolic demand.

Hair cells are organized into 3 rows of outer hair cells, and 1 row of inner

hair cells. Inner hair cells send auditory information to the brain, while outer hair cells act to stabilize or intensify the vibrations transmitted throughout the cochlea.

ear hair

� Red blood cells, possess concave surfaces, an adaptation that enhances surface area. At the nanolevel, the level at which all biochemistry occurs, increased surface allows for a greater number of substrates to participate in reactions that are mediated by nanoscale catalytic proteins known as enzymes.

Natural Perspective

Inorganic Perspective

� Inorganic catalysts

� Bulk gold is noble metal, inert to oxidation and other reactions.

� Nanoscale gold, is capable of catalyzing chemical reactions.

The properties of materials can be created and improved either by confining their dimensions in the nanoscale or by controlling their nanostructure.

Three-dimensional rendering of STM height images of gold nanoparticles. a,Decanethiol/MPA (2:1 molar ratio) showing ripples and b, OT/MPA (10:1 molar ratio) showing packed,phase-separated domains but not ripples.c,d,Schematic drawings of a and b,respectively. A. Jackson, et al, Nature Materials, vol3(2004) P330-336

Bulk physical example of a surface effect

� Sublimation is the conversion of a solid directly to a gas without an intermediate liquid phase.

� If ice sublimates at a rate of 1cm/h (T<0oC, low pressure condition), (a) how long would it take a cube of ice with volume of 1m3 to disappear? (b) for a sphere with the equivalent volume?

Properties

Properties

Melting point - 1064°°°° C

Melting Point of Gold

Properties

Properties

Properties

Modern Use of Nanoparticles: Biosensors

Nanoparticle Biosensor

The most familiar example of nanoparticles in sensing is the home pregnancy test.

Certain brands use gold nanoparticle aggregation to create a colormetric response. Nanoparticles (< 50 nm) are bound to antibodies complementary to a hormone produced by pregnant women. Latex microspheres are also bound to antibodies for the hormone. When the stick is submerged in urine flow, if the hormone is present it will bind to the microspheres (~ 500 µm) and nanoparticles causing aggregates to form. The solution then passes through a paper filter. If the pregnancy hormone is present, the aggregates will be trapped by the filter producing a colored product. If the pregnancy hormone is not detected, the nanoparticles will pass through the filter because of their small size.

Electrical Properties:Tunneling Current

Electrical Properties:Tunneling Current

Properties

Superparamagnetic Effect

Giant Magnetoresistance

Spintronics

challenges

� Integration of nanostructures and nanomaterials into or with macroscopic systems

� Building and demonstration of novel tools to study at the nanometer level what is being manifested at the macro level

� Other challenges:

such as: Doping in semiconductor-random doping fluctuations

Fabrication and Processing:

� Overcome the huge surface energy

� Ensure all nanomaterials with desired size, uniform size distribution, morphology, crystallinity, chemical composition, and microstructure, that altogether result in desired physical properites

� Prevent nanomaterials and nanostructures from agglomeration as time evolutes

Potential

� The ultimate small storage particle

� The ultimate small motor

� The ultimate small flying machine

� The ultimate small decision-making machine

� Robotic nanosubmarine for repairing the human body

� Self repairing cell

� ……..

Ethical implications

Legal implications

Environmental implications

Summary