Exercise 3.4-1

Quick Questions to

3.4 Structure, Interface and Some Properties

Here are some quick questions:
What is epitaxial growth? Consider the possibility of epitaxial growth; giving possible conditions (e.g. with respect to structures, lattice constants, ...) and use simple pictures:
  • A on A.
  • A (fcc) on B (fcc).
  • A (fcc) on C (hex).
  • A (fcc) on B (fcc) with intermediate layer.
  • ....
B (fcc; (100)) with lattice constant aA is deposited on A (fcc; (100) with aB = 0.95 aA. Sketch the structure for
  • Thickness of B only a few atomic layers.
  • Thickness of B > 50 nm
Difficult! Sketch a pure edge misfit dislocation network on a {100} interface plane for a misfit of 10 % for the case of
  • Burgers vector of the dislocations is b = a<100>.
  • Burgers vector of the dislocations is b = a/2<110>.
Difficult! What would happen if the (square) network of misfit dislocations on a {100} type interface would be changed from edge dislocations to screw dislocations?
What are the energetic reasons for introducing misfit dislocations into epitaxial interface it the layer thickness is larger than a critical thickness? What determines the critical thickness?
Sketch the curve for the critical thickness dcrit in a dcrit - misfit diagram, Try to give approximate numbers.
Enumerate and discuss structures obtainable with thin films but not (easily) with bulk materials. Give examples for applications.
Give reasons why thin film properties can be quite different from bulk properties; give examples.
Name some technologically extremely important special thin film properties; discuss with actual numbers.
     

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