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Published byKolby Pottinger Modified over 3 years ago

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Topical lecture: Quantum Size Effects in Nanostructures A. Tavkhelidze Ilia State University

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Contents Quantum mechanical tunneling and applications Quantum wells and super lattices Quantum wires and quantum dots (applications) Carbon nanotubes Graphene

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Quantum mechanical tunneling Where hbar is the Plank’s constant, d is barrier width, m is the electron mass, and U is the height of the potential barrier.

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Tunnel diode

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I-V characteristic of forward based tunnel diode Applications for tunnel diodes included local oscillators for UHF television tuners, trigger circuits in oscilloscopes, high speed counter circuits, and very fast-rise time pulse generator circuits.

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Josephson juction Main applications: SQUIDs Millimeter wave detectors and mixers Voltage standards

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Scanning tunneling microscope (STM)

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Coulomb blockade T<1 K

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Single electron transistor

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Problem 1 Why samples are cooled down in the scanning tunneling microscope?

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Quantum wells and super lattices

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Super lattice

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Quantum well applications

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Quantum wires and dots

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Electron inside the quantum dot

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Quantum dot solar cell

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Problem 2 Why electron wave function should equal to zero at the object boundary?

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Carbon nanotubes ArmcharZigzag Triple-walled armchair

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Carbon nanotube propertyes Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively Standard single-walled carbon nanotubes can withstand a pressure up to 24GPa without deformation. All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis.

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Graphene Carbon carbon bond length 0.142 nm Interplanar spacing 0335 nm The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov at the University of Manchester "for groundbreaking experiments regarding the two-dimensional material graphene

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Band structure of for arm-chair orientation

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Band structure of for zig-zag orientation

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Problem 3 Why such hard material as graphite in your pencil easily transfers to the paper when you write?

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Thank you for attention!

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