2. 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
3. What is Nanotechnology?
Nanotechnology is the creation and use
of materials or devices at extremely
small scales.
1 nm = 0.000000001 m
4. 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
5. 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)
6. 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.
7. 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
8. 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
9. 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
10. A Study and Analysis of
Blue Morpho Butterfly Wing
Nanostructures for
Commercial Fabrication
11. 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.
12. 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
13. Applications
Researchers intend to developed adequate fabrication methods for
commercial uses:
• Cosmetics • Paints
• Clothing • Fabrics
• Encoding in Fiber Optics • Integrated Optics Components
• Inhibition of Spontaneous Emission • Computer Circuits*
The Blue Morpho Rhenetor Butterfly
The Blue Morpho Rhenetor Butterfly is the
focus of our project as we study the
photonic crystals found on the scales of
the wings.
14. Finite-Difference Time-Domain (FDTD) Program
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
FDTD Model Recorder Layer
Top The white light enters the Data is displayed in a
PML source layer. curve plot.
The white light scatters The recorder layer detects
randomly across the which colors are reflected.
nanostructure.
Source Field
The nanostructure
PML absorbs light. behaves as a
Bottom
PML wavelength-dependent
Nanostructure mirror.
15. The FDTD modeling program uses Maxwell’s curl equations
for source-free materials:
r r
r ∂H r ∂E
∇× E = −µ (1) and ∇× H = ε (2).
∂t ∂t
r r
E 1 ∂H r n 2 ∂E
If E = , then × E = −
∇ (3) and =
∇× H
(4). η0 c0 ∂t c0 ∂t
Vectors E and H are then, written in their vector
components.
∂ Ez ∂ E y 1 ∂H x ∂Ex ∂Ez 1 ∂H y (6) ∂E y ∂Ex 1 ∂H z (7)
− =− (5) − =− − =−
∂y ∂z c0 ∂ t ∂z ∂x c0 ∂t ∂x ∂y c0 ∂t
∂ H z ∂ H y n 2 ∂ Ex ∂ H x ∂ H z n2 ∂ Ey ∂H y ∂ H x n 2 ∂ Ez
− = (8) − = (9) − = (10)
∂ y ∂ z c0 ∂ t ∂ z ∂ x c0 ∂ t ∂x ∂ y c0 ∂t
16. The derivatives in can be approximated as:
∂ Ex Ex ( t + ∆ t ) − Ex ( t ) ∂ Hand z ( y + ) − H ( y− )
∆y ∆y
H .
≅ ( RHD ) z
≅
2 z 2
( CD )
∂t ∆t ∂y ∆y
These derivatives are plugged into each of the E and H vectors
components to create update equations. For (8),
Ex ( t + ∆ t ) − Ex ( t ) c0 H z ( y + ) − H ( y − )
∆y ∆y
2 z 2
= 2
∆t n ∆y
c0 ∆ t H z ( y + 2 ) − H z ( y − 2 )
∆y ∆y
Ex ( t + ∆ t ) = E x + 2 (11).
n ∆y
The FDTD algorithm works by continuously forcing Maxwell’s
curl equations over the duration of the model.
18. 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!!!
19. 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
20. Benefits of Nanotechnology
In the computer world,
nanotechnology is important
to the development of small
computer circuits that can
reduced the size of
computers.
21. 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
23. 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.
24. 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.
Nanotechnology deals with the development and use of materials or devices in sizes ranging between 1 to 100 nanometers (nm). This range is known as the nanoscale . All materials that fall along this scale are known as either nanocrystals and nanomaterials .
The concept of nanotechnology was first introduced by American physicist Richard P. Feynman ( 1918-1988). Known for his contributions in quantum electrodynamics, he did this. Although never coining the term “nanotechnology”, Dr. Feynman successfully predicted several aspects and advancements in the field, including the use of advanced microscopes used to view materials at extremely small sizes, as well as the development of new fabrication methods. Feynman also discussed the possibility of atom-by-atom assembly , or the building of structures from individual atoms precisely joined by chemical forces. The concept of a “universal assembler” was derived from such a possibility in which a robotic device at nanoscale dimensions that could assemble atoms to create molecules of a desired chemical compound. Carbon atoms, for example, could may in the future be manipulated to fabricate low-cost diamonds.
There are three main tools used in the field of nanotechnology: transmission electron microscopes, atomic force microscopes, and scanning electron microscopes.
The transmission electron microscope is one that utilizes a high-energy electron beam that probes sample materials with a thickness less than 100 nanometers (nm). While some electrons are either absorbed or bounced of the material, others pass through it creating a magnified image as the one shown in the example. Current TEMs use digital cameras placed behind the material to capture and record images, magnifying images up to 30 million times. The TEM is the most popular microscope used the make images published in scientific journals on nanocrystals found in semiconductors.
The atomic force microscope (AFM) uses a small silicon tip as a probe to make images of sample material. While the probe move along the surface of the sample, the electrons of the atoms in the material begin to repel the electrons of the probe. The AFM then adjusts the height of the probe to keep the force of the sample constant. A mechanism records the movement of the probe and sends this information to a computer that will generate a three-dimensional image as shown in the slide. The image will show the exact topography of the surface.
A scanning tunneling microscope (STM) uses a wavelike property of electrons known as tunneling , which allows electrons emitted from a probe to penetrate, or tunnel into, the surface of the examined object. The electrons generate a tiny electric current that the STM measures. Similar to the atomic force microscope, the height of the probe in the STM is adjusted constantly to keep the current constant. In doing, so a detailed map of the material’ surface is produced as the example in this slide shows.
These microscopes can not only be used for imaging, but they also could be used in the manipulating of nanomaterials. In AFMs and STMs, the probes in these machines are used as “arms” of some sort to move around atoms of a particular structure. The image in this slide was produce by scientists at IBM, as they positioned 48 iron atoms into a circular structure using an STM. To keep these atoms at their respective positions, the conditions of the atoms’ environment were set at temperatures set near absolute zero (-273.15 ºC ), the theoretical temperature in when all motion (especially in atoms) completely stops.
This past summer, I participated in a research program for undergraduates at the University of Central Florida in Orlando, Florida. The research topic I was assigned ties in with the field of nanotechnology. The abstract in the next slide give a brief description of the project.
Photonic crystals are periodic dielectric nanostructures that affect the propagation of electromagnetic waves. They allow and forbid certain electron energy bands. 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 electromagnetic waves and allows them to operate in the visible portion of the spectrum. The following pictures shown are those photonic crystals that are found in nature. They include the opal gemstone, the sea mouse, the feathers of a peacock, and most specifically, the wings of a butterfly.
Researchers have strived to come up with the proper fabrication methods to synthesize these photonic crystals. At that point, we can hope to use these methods for commercial uses. The methods cold be used to hopefully produce paints, cosmetics, and fabrications. The manipulation of nanomaterials have already been proven to develop computer circuits. Meanwhile, in our project, the Blue Morpho Rhenetor Butterfly was studied as its iridescence sparked our interest.
The goal of the project was to gain images of cross sections cuts of the wing’s nanostructures. At which, the images were to be put to a MATLAB program that would perform what is called finite-difference time-domain modeling. The program simulates the natural phenomenon that takes place when light strikes nanostructures of the wings. The flowchart describes what happens in each step of the program.
Equations (1) and (2) are two of Maxwell’s curl equations that, for the most part, deal with the electromagnetic fields of source-free materials. With all substitutions, vectors E and H are then written in their components.
From there, more substitution is involved where the derivative in each component is approximated as shown above. They are plugged in the each of the components and the results are included in the FDTD algorithm to produce a model of the color distribution of the wing. The above example shows the substitution for equation (8) in the previous slide.
The result of the program is the following model of the program. The results basically show the reflection of the colors, measuring which wavelengths are absorbed and which ones and deflected. Those wavelengths that are reflected are those that are seen on the surface of a butterfly wing. The results shown are not accurate since the images were taken from a scientific journal.
Computer circuits are small pieces of semiconducting material with an electrical circuit consisting of what could be as many as millions of transistors. Usually at developed in sizes less than 5 cm, they assist in the overall functionality of computers, making them faster, compact, and most importantly, inexpensive. These computer circuits could be used in the computer for the central processing unit or for memory chips.
Computer circuits are made of semiconducting material , or material that is neither a good conductor or insulator. The most common semiconductor material used for computer circuits is silicon. Manufacturers usually take a sample of ultrapure silicon and slice them into thin wafers and covered with a light-sensitive coating. A template is then projected on the onto the wafer with intense ultraviolet light. The parts of the wafer still exposed to are showered with gases and ions to create transistors which are connected when metal is laid and insulated.
The world of computer technology can benefit from the development in nanotechnology as it can drastically reduce the size of computer circuits used in the overall functionality of a computer console. A F-100 microprocessor, for example, with its 0.6 x 0.6 cm size can fit through an eye of an needle. Meanwhile, a timeline is show from the year 1946, when the ENIAC (Electronic Numerical Integrator And Computer), the first fully electronic digital computer. The ENIAC weighed more than 30 tons, occupied 1800 square feet, and consumed 175 kw of power. Nanotechnology in the computer world later progressed the development of microprocessors as they allowed for smaller, compact desktop computers popularized in the early 1980s, and soon allowed laptop computers to be presented throughout the early and mid-1990s
The one major disadvantage in the handling of nanomaterials is its environmental dangers it may pose. Recent studies have shown that the release of particles into the environment point to possible carcinogen properties that may cause cancer, particularly in carbon nanotubes. Fortunately enough, a good number of products involving nanotechnology-based parts are bounded with other materials or components that keep its particles from floating freely. Meanwhile, officials urge for regulations to be placed to minimize any harmful threats.
Most lower-level computer science classes at Spelman, as well as most accredited institutions in some sense talk about nanotechnology. Whether if the subject is topically discussed, or if inventions of nanotechnology is briefly discussed in class, lower-level classes in some way touch up on how nanotechnology is applied to the world of computer science.
