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ZnO2 (Zinc oxide)

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Nano Lett., Vol. 4, No. 4, 2004 Nanostructures of zinc oxide. Zhong Lin Wang. Materials Today, June 2004. Photonic band structure of ZnO photonic crystal slab laser. – PowerPoint PPT presentation

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Title: ZnO2 (Zinc oxide)


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ZnO (Zinc oxide)
  • by
  • Alexander Glavtchev

3
Why is ZnO interesting?
  • Widely used
  • medicinal purposes (colds, rashes, antiseptics,
    sunscreen lotions)
  • used in manufacturing of rubber as rubber cure
    (or as filler)
  • pigment for paints and coatings
  • in electronics, used mainly in laser diodes,
    LEDs, transparent thin film coatings, and
    various piezoelectrics
  • Bright future
  • shows promising signs in the field of
    nanotechnology, UV detecors, nanoscale detectors
    and actuators
  • direct bandgap semiconductor that could replace
    silicon as the main substrate in chip
    manufacturing (if it can be easily/cheaply
    p-doped)
  • dual semiconductor and piezoelectric properties!!

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Properties
Melting Point 1975 C High electron mobility
gt100cm2/Vs High exciton binding energy 60meV
(electron-hole binding energy) Direct bandgap
3.3eV
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Piezoelectric Properties
The output amplitude is related to the input
signal by
Lithium niobate (LiNbO3) and Lithium tantalate
(LiTaO3) are currently two very-widely used
piezoelectric crystals due to their high
piezoelectric strain coefficients.
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Piezoelectric Properties
  • Can produce voltage output from applied stress
    (strain), or produce stress when voltage is
    applied.
  • Nanobelts and various nanoscale features of ZnO
    give higher piezoelectric constants (likely due
    to less dislocations and the impurity-free
    single-crystalline structures).
  • Piezoelectrics used in sensors (acoustic and
    electronic, as pickups in electric guitars,
    detection/generation of sonar waves, etc.)
    actuators (high-precision motors, loudspeakers,
    atomic force microscope probe control) possible
    future use in vibration and noise reduction
    (housing, automobiles).

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Semiconductor Properties
  • Zinc oxide is a direct wide-bandgap semiconductor
    (3.3-3.4eV).
  • Allows for efficient photon emission, as in LEDs
    or laser diodes (rather than phonon emission with
    energy loss and heat generation).
  • Can easily be n-doped with aluminum, indium, or
    extra zinc.
  • Possesses high electron mobility and
    photoconductivity can help speed up currents in
    semiconductor devices.
  • Drawbacks
  • p-doping is currently very difficult and
    inefficient and has prevented mass manufacturing
    of ZnO-based wafers.
  • High-purity ZnO grown on substrates other than
    sapphire has been challenging.

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Nano-Structures
  • Zinc oxide shows great potential for nanoscale
    electro-mechanical fabrication.
  • Highly-symmetric, singly-crystalline nanoneedles,
    nanowires, nanobelts, nanorings, nanohelixes,
    nanocombs, etc.
  • Hexagonal (wurtzite) structure helps
    lattice-matching and controlled growth.
  • Positive Zn surfaces and negative O surfaces
    create electric dipoles that facilitate
    polarization growth along certain directions and
    planes under applied voltage and temperature.

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Nano-Structures
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Summary
  • ZnO displays dual semiconductor and piezoelectric
    properties.
  • Used in laser diodes and LEDs.
  • Potential to be used as a wide-bandgap
    semiconductor.
  • Widely used in many other fields (medicine,
    farming, pigments).
  • Zinc oxide nanostructure growth is heavily
    researched presently.
  • The substance likely has the largest variety of
    nanostructures (and their associated properties)
    among all known materials.
  • Its hexagonal lattice can easily match
    catalysts lattice structure and facilitate
    controlled growth patterns.
  • Structures like nanowires, nanobelts and
    nanorings are of great interest in photonics
    research, optoelectronics, nanotechnology, and
    biomedicine.

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Sources
  • Nanoarchitectures of semiconducting and
    piezoelectric zinc oxide. JOURNAL OF APPLIED
    PHYSICS 97, 044304 s2005d
  • Piezoelectric Characterization of Individual Zinc
    Oxide Nanobelt Probed by Piezoresponse Force
    Microscope. Nano Lett., Vol. 4, No. 4, 2004
  • Nanostructures of zinc oxide. Zhong Lin Wang.
    Materials Today, June 2004.
  • Photonic band structure of ZnO photonic crystal
    slab laser. JOURNAL OF APPLIED PHYSICS 98, 103102
    2005
  • Deformation-Free Single-Crystal Nanohelixes of
    Polar Nanowires. Nano Lett., Vol. 4, No. 7, 2004
  • Zinc oxide hexagram whiskers. APPLIED PHYSICS
    LETTERS 88, 093101 2006
  • Zinc Oxide Nanostructures Growth, Properties and
    Applications. J. Phys. Condens. Matter 16 (2004)
    R829R858
  • Nitrogen doped zinc oxide thin film.
    http//repositories.cdlib.org/lbnl/LBNL-54116,
    2003
  • www.wikipedia.com
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