Lecture 10 - Diffusion Flashcards
What is diffusion
The mass of transport of particles (atoms, ions, molecules, electrons …) via a random mixing process
Why can solids migrate
As atoms are in constant motion
What is interdiffusion
In an alloy, atoms tend to migrate from regions of high concentration, to regions of low concentration.
What is self- diffusion
Is diffusion in one component material, when all atoms that exchange positions are of the same type
What is annealing
Where a material is heated (increases diffusion) and slowly cooled down
What does annealing help to reduce
Defects
What happens in vacancy diffusion
Atoms exchange with vacancies
Also apply to substitional impurities atoms
Rate dependent upon - N.O of vaccancies (defects) - may increases at elevated temperature
Activation energy to exchange
What do interstitial diffusion diffuse
Smaller atoms diffuse between larger atoms
Why is interstitial diffusion more rapid than vacancy diffusion
Interstitial are smaller more mobile
Many more empty interstitial positions available
Why do you dope semiconductors
To deliberately change its conductivity
