Molecular Beam Epitaxy






















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Atomic Force Microscope

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Atomic Force Microscope: Principle, Parts, Uses The atomic force  microscope  (AFM) is a type of scanning probe microscope whose primary roles include measuring properties such as magnetism, height, friction. The resolution is measured in a nanometer, which is much more accurate and effective than the optical diffraction limit. It uses a probe for measuring and collection of data involves touching the surface that has the probe. An image is formed when the scanning probe microscope raster-scans the probe over a section of the sample, measuring its local properties concurrently. They also have piezoelectric elements, which are electric charges that accumulate in selected solid materials like  DNA , biological proteins, crystal, etc, to enable tiny accurate and precise movement during scanning upon an electric command. The Atomic Force Microscope was invented in 1982, by scientists working in IBM, just after the invention of the Scanning tunneling Microscope in 1980 by Ge...
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Resonant Tunneling Diodes (RTD)

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Concept of Resonant Tunneling An interesting phenomena occurs when two barriers of width a separated by a potential well of a small distance 𝐿 as shown in fig. This leads to the concept of resonant tunneling. Fig.: Double barrier junction with no applied bias.   The barriers are sufficiently thin to allow tunneling and the well region between the two barriers is also sufficiently narrow to form discrete (quasi-bound) energy levels. The transmission coefficient of the double symmetric barrier becomes unity. (ie., T = 1) , when the energy of the incoming electron wave ( 𝐸 ) coincides with the energy of one of the discrete states formed by the well. Thus, transmission probability of the double symmetric barrier is maximum; hence, the tunneling current reaches peak value when the electron wave's energy is equal to the well's quantized energy state. This phenomenon is known as resonance tu...
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