Quantum Dots

S-104.3610 NANOTECHNOLOGY

Exercise 3 Home exercises (return 24th of Nov.):

24.11.2010

1. Explain briefly (Remember that sometimes a picture is worth a thousand words): a.) Ostwald ripening in ion implantation process b.) Laser ablation c.) Biolabeling d.) Photoluminescence e.) Molecular electronics f.) Coulomb blockade

2. There are plenty of biological applications of quantum dots. Choose one interesting application, try to find some literature related to it and let the rest of us know how it works. A Good way to start is to read through the following review article: “Biological Applications of Quantum Dots”, T. Jamieson et al., Biomaterials Vol 28, Issue 31, November 2007, page 4717.

Demo exercises: 1. Calculate three lowest transition energies between states in conductance and valence bands of a parabolic InAs quantum dot. The estimated harmonic potential for both bands are shown in the figure. The effective mass of the electron and * * the hole is chosen as me = 0.04m0 and mh = 0.12m0 , respectively, where m0 is a free electron mass. The effective gap of the InAs quantum dot potential (due to InAs bandgap, strain effects, and quantum confinement in vertical zQD direction) is Eg = 1.00 eV. (Hint: The allowed transitions are between the levels with the same quantum number in conductance and valence bands)

V(x

0.20

10 nm

x

E

QD g

= 1.00

0.10

2. Many of the nanocomposites have demonstrated technological importance and there’s plenty of literature available from the applications. What kind of applications there are and what are the advantages from nanocomposites in each case.

3. Consider a close-packed opal photonic crystal structure made of PMMA spheres (diameter D = 268 nm) arranged in fcc lattice. The refractive index of PMMA is 1.49 and the spheres are surrounded by air. Optical reflectance shows a maximum (and transmittance minimum) at the photonic band gap in the hkl = 111 direction. Calculate this wavelength.

θ

dhkl...