Nano Analys!

TEM – Transmission Electron Microscopy An microscope where electrons are transmitted through the sample and detected below.

SEM – Scanning Electron Microscopy An microscope where electrons are backscattered or emitted and detected above the sample.

STEM – Scanning Transmission Electron Microscopy An microscope where electrons are transmitted through the sample and detected below, while beam is scanned across the sample.

Diffraction Electron scattering

Elastic scattering When an atom changes the direction of an traveling electron due to forces from its nucleus

Inelastic scattering A fundamental scattering process in which the kinetic energy of an incident particle is not conserved

Secondary electrons Usefull electron scattering for identifying topography in SEM

Auger electrons Ejection of an outer-shell electron. These electrons have energy of ~few hundred eV to few keV and are much more strongly absorbed than characteristic X-rays.

Cathodoluminescence In direct-gap semiconductors, inelastic collisions may excite electrons from the valence to conduct band (creation of electron-hole pairs)

Coherent scattering Electrons scatter at low angels in the outskirts of the electron cloud

Incoherent scattering Electrons passing close to nucleus, stronger scattering

Thermionic emitter When a material is heated enough it will emit electrons

Field emitter Electrons are emitted when a voltage is applied to a small point. Exists cold and thermal (Schottky) emitters

Accelerating voltage The energy electrons need so they can travel through the microscope and into (or through) our sample

Condenser lenses An array of electric magnets that form a magnetic field to focus the electron beam in a microscope

Objective lens An array of electric magnets that form a magnetic field to focus, enhance and magnify the electron beam of a sample. IN TEM it is used to focus the beam on the sample

Intermediate and projector lenses An array of electric magnets that form a magnetic field to magnify the image onto a detector

Parallel (electron) beam A beam of electrons where electrons are moving parallel to eachother (low intensity)

Converged beam A beam of electrons that are focused onto a single point (high intensity)

Spherical aberration When a lens is improperly made so that the focalpoint differs depending on where you hit the lens

Chromatic aberration When the wavelenghts of particles highly determines the phase shift in the lens causing the focal point to be different for each wavelenght

Backscatter electrons detector (BSE detector) A detector sensitive to high angle electrons in a SEM. Often creates an image with a strong shadeing effect

Secondary electrons detector (SE detector) A detector capable of detecting electrons scattered. Great for topography

Excitation Volume The approximate map of where an electron travels inside of a sample

“Conventional” TEM (CTEM) A TEM technique where the sample area is obsereved all at once instead of scanning the sample piece by piece

Object plane An object as observed before a lens

Focal point The point of which all light from a lens converge. Here we have the highest resolution in a microscope

Image plane Object as seen through the lens

Contrast Difference in intensity

Mass-Thickness Incoherent scattering (nuclear scattering) scales with atomic number and can effect intensity of electrons. What contrast?

Diffraction contrast If a material is crystalline, small changes in orientation strongly affects the diffraction of electrons. What contrast?

Phase contrast When an electron travels through a material and the phase shift is observed. exploits differences in the refractive index of different materials. What contrast?

Aperture A disk with a hole in it. Restricts the amount of particles observed by a detector.

Constructive interference When the maxima of two waves add together

Deconstructive interference Where two waves are completely out of phase. Adding them together would cancel out the wave

Bragg condition When the sample is tilted at a correct q so Bragg’s law holds for a specific set of planes

Objective aperture By placing the apature at the correct spots above the sample one can selectivly single out a wavelength of electrons

Bright field imaging Observing electron intensity were the detector i placed right under the sample to detect the most intense electrons

Dark field imaging Observing electron intensity so that the detector is placed as far to the side as possible. This detects the most scattered of electrons

High Annular Dark Field Detector (HAADF) A detector used to select electrons scattered at very high angels

Aberration corrector A lens that can correct aberration in lenses

Phase-contrast HRTEM images Images taken with a electron microscope. They do not contain mass-thickness contrast on an atomic scale but do give highly accurate crystal structure information

Quasicrystal A structured that is ordered but not periodic

Translational symmetry Diffractionpattern stays the same evevn if moved (only x-axis and y-axis and without rotation)

Wave interference Waves that does not share the same phase or wavelength that interact

Bragg diffraction Encompasses the superposition of wave fronts scattered by lattice planes, leading to a strict relation between wavelength and scattering angle

Reciprocal space The reciprocal lattice represents the Fourier transform of another lattice

Lattice Set of points

Powder diffraction rings Small crystallites have random orientation which gives way for multiple diffractionpatterns to overlap and make a ring-shape

X-ray diffraction Scattering of photonsof crystals, powder diffraction pattern, and large crystals.

Electron diffraction Diffraction in form of electrons traveling through a thin sample

X-ray detector A detector sensitive ONLY to composition, no topographic information of the sample

Click

Type

Listen

Games

Print