14.3: Evaporation Techniques

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Simple Resistance Evaporation

The source (known as the charge) is held in an electrically conductive boat or crucible, supported in a coil, or wrapped around a rod. This support is then heated by passing a current through it.

This method is reliable and relatively cheap due to the lack of complex components. However, the heating of the support can lead to desorption / evolution of impurities which will be incorporated into the growing film. There is also limited control over the temperature of the charge, and hence the deposition rate, so this technique is most widely used for non-critical applications.

Electron Beam Evaporation

In this scenario, the charge is heated directly using an electron beam.

Electron beam evaporation

This can lead to higher purity films since the crucible / support is not heated and may be water-cooled. There may also be some ionisation or activation of the depositing vapour flux as it passes through the electron beam.