Microscopy Resolution Magnification Image sizeObject size Resolution The
Microscopy & Resolution Magnification: Image size/Object size Resolution: The fineness of detail that can be distinguished in an image. Highest Typical Resolution Optical Microscope ~200 nm Electron Microscope ~0. 1 nm OU Nano. Lab/NSF NUE/Bumm & Johnson
Definitions • Acceptance angle θ θ • Numerical Aperture NA = n sinθ • Rayleigh resolution criterion for a circular aperture Δx = 0. 61 λ/NA OU Nano. Lab/NSF NUE/Bumm & Johnson
OPTICAL MICROSCOPES Image construction for a simple biconvex lens OU Nano. Lab/NSF NUE/Bumm & Johnson
Rayleigh criterion for resolution Numerical Aperature Resolution Rayleigh Criterion www. microscopy. fsu. edu ; www. imb-jena. de See more interactive tutorials at www. microscopy. fsu. edu OU Nano. Lab/NSF NUE/Bumm & Johnson
Bright. Field Comparison • Full aperture is illuminated OU Nano. Lab/NSF NUE/Bumm & Johnson Dark. Field • A central obstruction blocks the central cone.
Dark-Field Optical Microscopy • A central obstruction blocks the central cone. • The sample is only illuminated by the marginal rays. • These marginal rays must be at angles too large for the objective lens to collect. • Only light scattered by the object is collected by the lens. OU Nano. Lab/NSF NUE/Bumm & Johnson www. microscopy. fsu. edu
Dark-Field Optical Microscopy OU Nano. Lab/NSF NUE/Bumm & Johnson www. microscopy. fsu. edu
THE ELECTRON MICROSCOPE The wavelength of the electron can be tuned by changing the accelerating voltage. de Broglie : λ = h/mv λ: wavelength associated with the particle h: Plank’s constant 6. 63× 10 -34 Js; mv: momentum of the particle me= 9. 1× 10 -31 kg; e = 1. 6× 10 -19 coulomb P. E e. V = ½mv 2 λ = h/ (2 me. V) = 12. 3/ V (for V in KV, λ in Å) V of 60 k. V, λ = 0. 05 Å Δx ~ 2. 5 Å Microscopes using electrons as illuminating radiation TEM & SEM OU Nano. Lab/NSF NUE/Bumm & Johnson
OU Nano. Lab/NSF NUE/Bumm & Johnson
Components of the TEM 1. 2. 3. 4. 5. 6. 7. Electron Gun: Filament, Anode/Cathode Condenser lens system and its apertures Specimen chamber Objective lens and apertures Projective lens system and apertures Correctional facilities (Chromatic, Spherical, Astigmatism) Desk consol with CRTs and camera Transformers: 20 -100 k. V; Vacuum pumps: 10 -6 – 10 -10 Torr OU Nano. Lab/NSF NUE/Bumm & Johnson
Schematic of E Gun & EM lens Magnification: 10, 000 – 100, 000; Resolution: 1 - 0. 2 nm www. udel. edu OU Nano. Lab/NSF NUE/Bumm & Johnson
TEM IMAGES OU Nano. Lab/NSF NUE/Bumm & Johnson www. udel. edu ; www. nano-lab. com ; www. thermo. com
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