Quantum Dots

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Quantum Dots. KE – 31.5530 Nanopartikkelit 4.5.2011 Lauri Lehtola. Outline. Quantum dots structure Preparation methods Applications Excisting and visionary. http://www.lbl.gov/Science-Articles/Archive/Quantum-Dot-Electronics.html. Quantum dots. Nanocystals - PowerPoint PPT Presentation

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  • Quantum DotsKE 31.5530 Nanopartikkelit4.5.2011Lauri Lehtola

  • OutlineQuantum dotsstructure

    Preparation methods

    ApplicationsExcisting and visionaryhttp://www.lbl.gov/Science-Articles/Archive/Quantum-Dot-Electronics.html

  • Quantum dotsNanocystalsBoth atom and bulk-like propertiesCommonly made from semiconductor materials or heavy metals

    Research began in 1980sSmaller semiconductor devicesQuantum wells (2D), quantum wires (1D)DNA 1/2

  • Quantum DotsCurrent carriers are confined in all three dimensionsDimension size ~ electron wave lengthQuantum mechanical particle in a box situationSolution:

    Discrete energy levels

  • Quantum DotsDiscrete energy levelsFluorescence

    Controlling of energy gapsSmall size high gap high energyDifferent wavelengths

    Tunable or man-made atomshttp://www.rsc.org/Publishing/ChemTech

  • Quantum DotsEasily in situ alterableEnergy level structureModified with voltage

    Magnetic phasesControlled with external magnetic fields

    Electrical, catalyst propertiesOnion-like architecture, etc.

    http://www.enc.edu/~john.u.free/

  • PreparationChemical synthesis from colloidsPrecursor, surfactant, solventTypical precursors: CdSe, CdS, InAs

    Correct temperature and precursor concentrationHighly monodisperse particles

    Commercially used methodhttp://www.nanocotechnologies.com/

  • PreparationSelf-assembling during molecular beam epitaxyQuantum dots on a surface

    Stranski-Krastanov growthCertain layer thickness islands nucleatehttp://www-thz.physics.ox.ac.uk/publications.html

  • PreparationNew cheaper and faster methods

    Restrictions of using heavy metals

    Room temperature preparationSonochemical Synthesis http://pubs.acs.org/doi/full/10.1021/cm0505547

  • ApplicationsSolar cellsTraditional cells: excess kinetic energyThis energy is lost soon

    Quantum dot coating

    Multiple excitons from a single photon

    MEG (Multiple Exciton Generation)http://www.nanoprinttech.com/quantum_dot.html

  • ApplicationsBiological trackingTag molecules with quantum dotsOnly particlular molecules

    Processes inside living cells

    Clusters of quantum dotsNo blinkinghttp://www.ieeeghn.org/wiki/index.php/Quantum_Dots

  • ApplicationsQLEDs and QLED displaysDirect utilization of electroluminescenceElectrons to photons

    Easy patterningInkjet printingPure colorsNo color masks smaller energy consumptionShort lifetime (10 000 h)

    http://www.physorg.com/news/2011-02-fabricate-large-area-full-color-quantum-dot.html

  • ApplicationsOther possibilities: Quantum computerQuantum dots as qubits

    Application: scientific toolTheoretical information of few-body effects in finite and reduced dimensionsAlready now new phenomenaNew phases, magnetic ground statesMore to come

  • ConclusionStructureConfined electrons and holes

    PreparationChemical, MBE

    ApplicationsVariety of ways to utilize