Nanotechnology/Additional methods

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Point-Projection Microscopes[edit]

Point-Projection Microscopes are a type of field emission microscope[1], and consists of three components: an electron source, the object to the imaged, and the viewing screen[2].

Low energy electron diffraction (LEED)[edit]

LEED is a technique for imaging surfaces, and has two principle methods of use: qualitative and quantitative. The qualitative method measures relative size and geometric properties, whereas the quantitative method looks at diffracted beams as a way of determining the position of atoms.

Reflection High Energy Electron diffraction[edit]

RHEED is similar to LEED but uses higher energies and the electrons are directed to the be reflected on the surface at almost grazing incidence. This way the high energy electrons only penetrates a few atomic layers of the surface.

X-ray Spectroscopy and Diffraction[edit]

X-ray Spectroscopy refers to a collection of techniques including, but not limited to X-ray Absorption Spectroscopy and X-ray Photoelectron Spectroscopy.

X-rays can be used for X-ray crystallography.

Auger electron spectroscopy (AES)[edit]

Auger Electron Spectroscopy is a technique that takes advantage of the Auger Process to analyze the surface layers of a sample[3].

Nuclear Magnetic Resonance (NMR)[edit]

  • Nuclear Magnetic Resonance (NMR) - in a magnetic field the spin of the nuclei of molecules will precess and in strong fields (several tesla) this happens with rf frequencies that can be detected by receiving rf antennas and amplifiers. The precession frequency of an individual nucleus will deviate slightly depending on the its surrounding molecules' electronic structure and hence detecting a spectrum of the radiofrequency precession frequencies in a sample will provide a finger print of the types of molecules in that sample.
  • Nuclear quadrupole resonance is a related technique, based on the internal electrical fields of the molecules to cause a splitting of the nuclear magnetic moments energy levels. The level splitting is detected by rf as in NMR. Its is used mainly for experimental explosives detection.

Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)[edit]

Electron Spin Resonance (ESR) measures the microwave frequency of paramagnetic ions or molecules[4] .

Mössbauer spectroscopy[edit]

Mössbauer spectroscopy detects the hyperfine interactions between the nucleus of an atom, and the ambient environment. The atom must be part of a solid matrix to reduce the recoil affect of a gamma ray emission or absorption[5].

Non-contact Nanoscale Temperature Measurements[edit]

Heat radiation has infrared wavelengths much longer than 1 µm and hence taking a photo of a nanostructure with e.g. a thermal camera will not provide much information about the temperature distribution within the nanostructure (or microstructure for that sake).

Temperatures can be measured locally by different non-contact methods:

  • Spectroscopy on individual quantum dots [1].
  • Spectra of laser dyes incorporated in the structure
  • Raman microscopy (the temperature influences the ratio of stokes and anti-stokes lines amplitude, the width of the lines and the position of the lines.)
  • Transmission electron microscopy can also give temperature information by various techniques [2]
  • Special AFM probes with a temperature dependent resistor at the tip can be used for mapping surface temperatures
  • Infrared Near-field Microscopy [6]
  • Confocal raman microscopy can provide 3D thermal maps [3]

References[edit]

See also notes on editing this book about how to add references Nanotechnology/About#How_to_contribute.

  1. Rochow, Theodore George, and Paul Arthur Tucker. "Emissions Microscopies". Introduction to Microscopy by Means of Light, Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
  2. The Future of the SEM for Image and Metrology
  3. Auger Electron Microscopy
  4. What is EPR?
  5. Introduction to Mossbauer Spectroscopy: Part 1
  6. C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, "Thermal Imaging by Infrared Near-field Microscopy," Proceedings of IEEE Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1, November 1996, pp. 249-250