1. MSN 510 Imaging Techniques in Materials Science and Nanotechnology
Instructor: Aykutlu Dana
UNAM Institute of Materials Science and Nanotechnology,
Bilkent, Ankara-Turkey

2. Course Organization Class outline Homeworks Laboratory Work
Extensive Matlab Simulations
Laboratory Work
Preparations
Laboratory
Laboratory Report
Groups of 4 People

3. 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

4. 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

5. 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)

6. 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
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

7. 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:

8. 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)

9. 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.

10. 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

11. 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.

12. 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.).

13. 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.

14. Huygen’s Principle (Approximation)
Each point on a wavefront acts as a point source

15. 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?)

16. 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