# Exercise 3.3-1

# Quick Questions to

## 3. Point Defects and Diffusion

| Here are some quick questions:
|  | The answers are sometimes (and possibly only indirectly) contained in the links.
| 3.1.1 Diffusion and Point Defects
|  | Give examples of products / processes / technologies that depend in a major way on point defect diffusion.
|  | Write down and discuss Fick's 1st law
|  | Write down and discuss Fick's 2nd law
|  | How do Ficks Laws connect to atomic diffusion? Give the two important equations dermining the diffusion coefficientD i) by atomic jumping, and ii) via the diffusion length L.
|  | What is the geometry factor g concerning jumping point defects in lattices? Can you give numbers for some common lattices?
| 3.2 Diffusion mechanisms
|  | Describe at least 2 possibilites for the diffusion of a substitutional and interstial impurity atom, respectively.
|  | Which diffusion mechanisms are the most important ones?
|  | For a substitutional impurity atom that diffuses via a vacancy mechanism, the diffusion coefficient D will be proprotional to ....?
|  | How do atoms diffuse in amorphous materials - e.g. glasses and polymers?
|  | What is self diffusion? The self-diffusion coefficient Dself is given by....?
|  | Any given atom in a given crystal will sooner or later leave its original place because of self diffusion. How long - roughly - does it take at high temperatures for all atoms to have changed positions? How about the atoms in your brain?

With frame

Solution to Exercise 3.1-1

3.1.1 Diffusion and Point Defects

3.2.1 Atomic Mechanisms

3.2.2 Self-Diffusion

Solution to Exercise 3.2-1

© H. Föll (Defects - Script)