Next Lecture

Physics of Thin Films

PES 449 / PHYS 549


Introduction and Overview

Ohring: Historical Perspective p. xix


What is a "thin film" ?

thin = less than about one micron ( 10,000 Angstroms, 1000 nm)

film = layer of material on a substrate

(if no substrate, it is a "foil")


Applications:

  • microelectronics - electrical conductors, electrical barriers, diffusion barriers . . .
  • magnetic sensors - sense I, B or changes in them
  • gas sensors, SAW devices
  • tailored materials - layer very thin films to develop materials with new properties
  • optics - anti-reflection coatings
  • corrosion protection
  • wear resistance
  • etc.


Special Properties of Thin Films:

different from bulk materials

Thin films may be:

  • not fully dense
  • under stress
  • different defect structures from bulk
  • quasi - two dimensional (very thin films)
  • strongly influenced by surface and interface effects

This will change electrical, magnetic, optical, thermal, and mechanical properties.


Typical steps in making thin films:

  1. emission of particles from source ( heat, high voltage . . .)
  2. transport of particles to substrate (free vs. directed)
  3. condensation of particles on substrate (how do they condense ?)

 

Simple model:

simple model of film deposition

How do the variables effect film structure and properties ?


What physics is in all this ?

  • thermodynamics and kinetics
    • phase transition - gas condenses to solid
    • nucleation
    • growth kinetics
    • activated processes
      • desorption
      • diffusion
    • allowed processes and allowed phases
  • solid state physics
    • crystallography
    • defects
    • bonding
  • electricity and magnetism
    • optics
    • conductivity - resistivity
    • magnetic properties
  • mechanics
    • stresses in films
    • friction and wear

- - - INDEX OF LECTURES - - - Next Lecture Next lecture