Nanotechnology

Nanotechnology and the Development of Computer Circuits

In this presentation…… Concept and History of

Nanotechnology Why Nanotechnology? Applications of Nanotechnology

Applications to Computer Circuits Benefits and Disadvantages of

Nanotechnology Connections with Computer

Programming

What is Nanotechnology?

Nanotechnology is the creation and use of materials or devices at extremely small scales.

1 nm = 0.000000001 m

Nanotechnology Foretold Concept first introduced by

American physicist Richard P. Feynman (1918-1988)

Calculated that an encyclopedia set could be compressed to fit the head of a pin.

Predicted several aspects in today’s nanotechnology

Advanced microscopes Developments in fabrication

methods Possibilities of atom-to-atom

assembly

Tools In Nanotechnology

The main tools used in nanotechnology are three main microscopes Transmission Electron Microscope

(TEM) Atomic Force Microscope (AFM) Scanning Tunneling Microscope (STM)

Transmission Electron Microscope (TEM) Uses high-energy

electron beam to probe material with thickness < 100 nm.

Some electrons are absorbed or bounced off object; some pass through the object and make magnified images

Digital camera records images.

Atomic Force Microscope (AFM)

Use small silicon tip as probe to make images of sample material

Probe moves along surface

Electrons of atoms in sample repel those in probe

Creates 3-D images

Scanning Tunneling Microscope (STM) Uses nanosized probe

to scan objects and materials

Uses tunneling to detect surface and creates a map of surface

Rate of electrons that tunnel from probe to surface related to distance between probe and surface

Other Uses for Tools Microscopes used for

imaging and manipulating nanostructures

“Arms” in AFMs and STMs used to move around individual atoms

Scientists at IBM made this image using an STM to with iron atoms into a circular structure

A Study and Analysis of Blue Morpho Butterfly Wing Nanostructures for Commercial Fabrication

Abstract

This study focuses on the photonic crystals found in the scales of a butterfly wing, particularly those of the species known as the blue Morpho Rhetenor butterfly. To study these nanostructures, scanning electron microscope (SEM) imaging and the development of a finite-difference time-domain (FDTD) program were necessary. The FDTD program produced a graphical display of what colors are reflected as a result of light propagation. The purpose of this study was to find what method of fabrication is necessary to possibly reproducing these photonic crystals. Such fabrication methods would eventually be applied for commercial uses.

What Are Photonic Crystals?

• Periodic dielectric nanostructures affecting propagation of EM waves; allows and forbids certain electron energy bands.• Give rise to such optical events as the inhibition of spontaneous emission and low-loss waveguiding when allowed propagating electromagnetic waves are not present. • The basic phenomenon behind photonic crystals is based on diffraction, or the bending and spreading of waves.• Periodicity of photonic crystal structures must be at the same length scale of the wavelength of the EM waves; allows them to operate in the visible portion of the spectrum.• Bragg’s Law: λB = 2neffΛ

Photonic Crystals Found In Nature• Opal • Sea Mouse • Butterfly• Peacock

Applications

Researchers intend to developed adequate fabrication methods for commercial uses:

• Cosmetics

• Clothing

• Encoding in Fiber Optics

• Inhibition of Spontaneous Emission

The Blue Morpho Rhenetor Butterfly

• Paints

• Fabrics

• Integrated Optics Components

• Computer Circuits*

The Blue Morpho Rhenetor Butterfly is the focus of our project as we study the

photonic crystals found on the scales of the wings.

Finite-Difference Time-Domain (FDTD) Program

Recorder Layer

Bottom PML

Top PML

Source Field

Nanostructure

FDTD ModelTop PML

FDTD Model

A finite-difference time-domain (FDTD) program was developed in MATLAB to simulate the photonic behavior of the nanostructures directly from the captured SEM images. This program simulates the natural phenomenon that takes place when visible light is incident on the nanostructures within the scales of the wings.

FLOWCHART

The white light enters the source layer.

The white light scatters randomly across the

nanostructure.

PML absorbs light.

The nanostructure behaves as a

wavelength-dependent mirror.

The recorder layer detects which colors are reflected.

Data is displayed in a curve plot.

The FDTD modeling program uses Maxwell’s curl equations for source-free materials:

HE

t

E

Ht

(1) and (2).

0

EE

0

1 HE

c t

2

0

n EH

c t

If , then (3) and (4).

0

1y xzE HE

y z c t

0

1 yx zHE E

z x c t

0

1y x zE E H

x y c t

2

0

y xzH EH n

y z c t

2

0

yx zEH H n

z x c t

2

0

y x zH H En

x y c t

Vectors E and H are then, written in their vector components.

(5) (6) (7)

(8) (9) (10)

RHDx xxE t t E tE

t t

2 2

CDy y

z zzH y H yH

y y

The derivatives in can be approximated as:

and .

These derivatives are plugged into each of the E and H vectors components to create update equations. For (8),

2 202

y yz zx x

H y H yE t t E t c

t n y

2 202

y yz z

x x

H y H yc tE t t E

n y

(11).

The FDTD algorithm works by continuously forcing Maxwell’s curl equations over the duration of the model.

Numerical Results

Computer Circuits Computer circuits are

small pieces of semiconducting material containing an electronic circuit.

Most commonly used in computers

Consists of as many as millions of transistors. Nanotechnology is

applied to the reduction in the size of

these computer circuits!!!

Methods of Developing Computer Circuits

The most common method of fabricating computer circuits is the top-down method Thin films of materials, which make

up a mask, are deposited on a silicon wafer

Unnecessary portions are etched off

Benefits of Nanotechnology

In the computer world, nanotechnology is important to the development of small computer circuits that can reduced the size of computers.

Disadvantages of Nanotechnology

Safety hazards with nanomaterials Some studies detected possible

cancer-causing properties of carbon nanotubes

Some nanomaterials bounded with other materials or components

Effects on Society

Connections with Computer Science

With the continual advancements and applications of nanotechnology to computer science, computers will surely improve drastically in the functionality, speed, and overall performance, as well as decrease in size providing more breathing room at home, at the office, or at school. These advancements have also begun to pave the way for portable devices such as MP3 players and PDAs. The world of computer science can only grow exponentially through the assistance of nanotechnologists. This topic interest me because I intend to focus my career in the research and development of nanodevices that affect the medical and computer science fields, as well as the everyday world in which we live.

Where Can We Learn More???

Most lower-level computer science courses at Spelman (and Morehouse) may touch up on nanotechnology, or at least speak of their overall contributions without actually using the term itself.

Bibliography