MSN 510 Imaging Techniques in Materials Science and Nanotechnology

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MSN 510 Imaging Techniques in Materials Science
and Nanotechnology

• Instructor Aykutlu Dana
• UNAM Institute of Materials Science and
  Nanotechnology,
• Bilkent, Ankara-Turkey

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Course Organization

• Class outline
• Homeworks
• Extensive Matlab Simulations
• Laboratory Work
• Preparations
• Laboratory
• Laboratory Report
• Groups of 4 People

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Why is microscopy important ?

• 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

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Why is microscopy important ?
The other nine advancements heavily rely on
microscopy Or are enabled by microscopy and
related techniques

• 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

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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)

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Some history (EM)

DATE NAME EVENT
1897 J. J. Thompson Discovers the electron
1924 Louis deBroglie Identifies a wavelength to moving electrons lh/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

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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/educationa
l_games/physics/microscopes/1.html
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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
  cross-sectional 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)

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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.

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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

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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.

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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.).

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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.
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Huygens Principle (Approximation)

• Each point on a wavefront acts as a point source

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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
Sinc squared (Fourier transform?)
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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
Sinc (Sin x)/x squared
square