Nano Lab (Lec2 SEM)

Nano Lab (Lec2 SEM) - Scanning Electron Microscopy (SEM)...

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Nano Lab MAE C187L/C287L Scanning Electron Microscopy (SEM) Nano Labs, MAE C187L/C287L
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Nano Lab MAE C187L/C287L Optical Microscopy
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Nano Lab MAE C187L/C287L Resolution of Optical Microscope Single Spot Mixed spot Resolved Spots d>λ d<<λ, a spot will become a ring The size of the ring will be determined by the spot size and the wavelength λ Resolution for a microscope R ~ 0.61 λ
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Nano Lab MAE C187L/C287L Resolution Limited by Wavelength R ~ 0.61 λ
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Nano Lab MAE C187L/C287L Electron is a Small Particle Discovery of electron Electron ray in vacuum tube Electron mass = 9.10938188 ×10 -31 kg Electron diameter < 10 -18 m
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Nano Lab MAE C187L/C287L Particle is Wave-like Davisson and Germer Experiment A wave passed through double slits will generate an interfering pattern, particles will not. Electron is wave!
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Nano Lab MAE C187L/C287L Why e-beam? The wavelength of electron beam λ (Ǻ)= 12.26/√E (eV) The resolution of a microscope δ = λ / Sin θ E (keV) λ (Ǻ) 10 0.122 100 0.037 1000 0.0087
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Nano Lab MAE C187L/C287L History The Transmission Electron Microscope (TEM) was the first type of Electron Microscope to be developed by Max Knoll and Ernst Ruska in Germany in 1931. The first Scanning Electron Microscope (SEM) debuted in 1942 with the first commercial instruments around 1965. Its late development was due to the electronics involved in "scanning" the beam of electrons across the sample. SEM and TEM are two of the major microscopes to observe the objects at nanoscale. Nobel Prize (1986)
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Nano Lab MAE C187L/C287L Scanning Electron Microscope The scanning electron microscope (SEM) is a type of electron microscope that creates various images by focusing a high energy beam of electrons onto the surface of a sample and detecting signals from the interaction of the incident electrons with the sample's surface with a resolution down to 1 nm.
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Nano Lab MAE C187L/C287L Scanning Electron Microscope Electrons are produced with an electron gun, similar to the one in a television. The electrons are then accelerated through the Anode plate and focused with the Magnetic Lens. The Scanning Coils force the electron beam to rapidly scan over an area of the specimen. The specimen can be viewed in the Backscattered or Secondary mode.
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Nano Lab MAE C187L/C287L Scanning Electron Microscope The electron optics ‘column’ produces a highly focused beam of electrons that impinges on a point of the specimen. The interaction of the beam with the specimen induces a signal that is sensed by the detector. The sensed intensity of the response varies as the beam is sequentially scanned over consecutive points of the specimen and this variation of intensity is recorded in the computer memory as a grayscale image.
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Nano Lab MAE C187L/C287L Different Electron Sources
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Nano Lab MAE C187L/C287L Magnetic Lens As an electron comes down the optical path, it first encounters the horizontal component (B R ) of the magnetic field. This causes the electron to begin a rotation about the axis. The
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Nano Lab (Lec2 SEM) - Scanning Electron Microscopy (SEM)...

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