Question 1.
a. What is a quantum wire?
b. Show that the confinement energy in an infinitely deep rectangular quantum wire is: Ex,z=?2π22m∗[ nx2Lx2+nz2Lz2 ]
c. Name and briefly explain three fabrication methods for quantum wires.
d. Name three potential applications for quantum wires.
Question 2.
a. What are quantum dots and what are their characteristics?
b. Using the particle-in-a-box-model for an electron in a quantum dot (for example, colloidal CdSe QDs in the size range 1- 10 nm) explain why larger dots emit in the red end of the spectrum, and smaller dots emit blue or ultraviolet light.
Question 3.
a. Name and briefly explain three applications of QDs.
b. Name and briefly explain three fabrication methods of QDs.
c. Which growth modes can be distinguished for heteroepitaxial growth, which factors determine the growth mode, and which mode is used for selfassembled growth of QDs?
Question 4.
Draw the energy band line-up for CdSe in contact with the following materials given the data below:
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CdSe:
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band gap 1.75eV
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electron affinity 4.4 eV
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Silica:
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band gap 9.0eV
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electron affinity 0.9 eV
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Indium tin oxide:
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band gap 3.75eV
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electron affinity 4.8eV (n-type)
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Nickel oxide:
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band gap 4.3eV
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electron affinity 1.8eV (p-type)
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Polyvinylcarbazole:
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band gap 4.90/
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electron affinity 1.2eV (p-type)
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Discuss how you might want to ensure carrier confinement in quantum dots made from CdSe if you were to make a structure with the dots at the centre of a p-n region.
Question 5.
Write a definition of the following in your own words (180-200) words: including references:
1) Volume plasmons - free electron materials
2) Van Hove singularities
3) quantum dot grown on an inverted pyramid, define: inverted pyramid
4) Frank-van-der-Merwe (FvdM) - two-dimensional layer-by-layer growth.
5) Volmer-Weber (VW) - three-dimensional island growth.
6) Stranski-Krastanov (SK) - layer-by-layer growth followed by the spontaneous nucleation and growth of islands.