MSN 510
Imaging Techniques in Materials
Science and Nanotechnology
Instructor: Aykutlu Dana
UNAM Institute of Materials Science and
Nanotechnology,
Bilkent, Ankara-Turkey
Course Organization
• Class outline
• Homeworks
– Extensive Matlab Simulations
• Laboratory Work
– Preparations
– Laboratory
– Laboratory Report
• Groups of 4 People
Why is microscopy important ?
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
The International Technology Roadmap for Semiconductors
Scanning probe microscopes
Giant magnetoresistive effect
Semiconductor lasers and light-emitting diodes
National Nanotechnology Initiative
Carbon fiber reinforced plastics
Materials for Li ion batteries
Carbon nanotubes
Soft lithography
Metamaterials
Why is microscopy important ?
The other nine advancements heavily rely on microscopy
Or are enabled by microscopy and related techniques
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
The International Technology Roadmap for Semiconductors
Scanning probe microscopes
Giant magnetoresistive effect
Semiconductor lasers and light-emitting diodes
National Nanotechnology Initiative
Carbon fiber reinforced plastics
Materials for Li ion batteries
Carbon nanotubes
Soft lithography
Metamaterials
Why is microscopy so important ?
The other nine advancements heavily rely on microscopy
Or are enabled by microscopy and related techniques
Example: Carbon Nanotubes (Iijima, 1991)
Some history (EM)
DATE
NAME
EVENT
1897
J. J. Thompson
Discovers the electron
1924
Louis deBroglie
Identifies a wavelength to moving electrons
l=h/mv
where
l = wavelength
h = Planck's constant
m = mass
v = velocity
(For an electron at 60kV l = 0.005 nm)
1926
H. Busch
Magnetic or electric fields act as lenses for electrons
1929
E. Ruska
Ph.D thesis on magnetic lenses
1931
Knoll & Ruska
First electron microscope built
1931
Davisson & Calbrick
Properties of electrostatic lenses
1934
Driest & Muller
Surpass resolution of the LM
1938
von Borries & Ruska
First practical EM (Siemens) - 10 nm resolution
1940
RCA
Commercial EM with 2.4 nm resolution
1945
1.0 nm resolution
Nobel Prizes
• 1903 – Richard Zsigmondy develops the ultramicroscope and is
able to study objects below the wavelength of light.
The Nobel Prize in Chemistry 1925
• 1932 – Frits Zernike invents the phase-contrast microscope that
allows the study of colorless and transparent biological materials.
The Nobel Prize in Physics 1953
• 1938 – Ernst Ruska develops the electron microscope. The ability to
use electrons in microscopy greatly improves the resolution and
greatly expands the borders of exploration.
The Nobel Prize in Physics 1986
• 1981 – Gerd Binnig and Heinrich Rohrer invent the scanning
tunneling microscope that gives three-dimensional images of objects
down to the atomic level.
The Nobel Prize in Physics 1986
To get a feeling: http://nobelprize.org/educational_games/physics/microscopes/1.html
What is an Image?
• Sample has a property distribution M(x,y,z)
• An image is a map of M(x,y,z) , or a 2D crosssectional map of M(x,y,z)
• A microscope is an instrument that generates a
data map from the small spatial scale property
distribution M(x,y,z).
• Resolution is a measure of dx, dy or dz of the
generated map for distinct points providing
complementary information (nonredundant)
What is an Image?
• Sample has a property distribution M(x,y,z)
• The property distribution may be related to
–
–
–
–
–
–
Density
Atomic number
Optical refractive index variation
Luminescent properties
Phonon density or energy
..... etc.
• We can image some specific property using an
appropriately chosen probe by measuring the
interaction of the probe with the sample at different
x,y and z locations.
• The dominant interaction of the probe with the
specific property will be instrumental in imaging
that property.
Example: Optical Light Microscope
• Probe: Light of certain spectral distribution
• Property to be imaged:
– Optical absorption of the sample
– Optical phase shifts due to refractive index
variations of the sample
– Luminescence properties of the sample
Parallel vs. Sequential Imaging
• In parallel imaging, generally the sample or the
probe is not scanned
• The whole sample area to be imaged is illuminated
by the probing wave in a uniform way.
• Scattering, absorption or other perturbations of the
wave take place at the sample.
• Probe signal, now carrying information about the
sample, propagates through the optical system
which reconstructs the image at the detector plane.
• Since image formation is done by fundamental
physics laws governing propagation of the probe
wave, for each point of the sample simultaneously,
we refer to this imaging method as parallel imaging.
Parallel vs. Sequential Imaging
• In sequential imaging, the sample or the
probe is scanned
• The probe has small diameter and interacts
locally with the sample.
• Interaction of the sample with the probe is
recorded as a function of x,y or z.
• Image formation is done by recording the
probe signal by secondary means
(computers etc.).
Parallel Imaging uses waves
• Acustic, Electromagnetic (Light), Electron
waves
• Wave equation (EM)
• Helmholtz Equation
– Harmonic waves: Separate in time and space
The paraxial approximation further simplifies math.
Huygen’s Principle (Approximation)
• Each point on a wavefront acts as a point
source
Near Field and Far field
• Near field: Right at the source
• Far field (Fraunhofer): At infinity (many
wavelengths away from the source)
propagation
We detect
energy of
the EM
wave
square
Sınc squared (Fourier transform?)
Near Field and Far field
• Huygens' principle when applied to an aperture simply
says that the far-field diffraction pattern is the spatial
Fourier transform of the aperture shape, and this is a
direct by-product of using the parallel-rays
approximation, which is identical to doing a plane wave
decomposition of the aperture plane fields
propagation
square
Sinc [=(Sin x)/x] squared