There are several types of ion sources, and the most commonly used are Kaufman ion source and its improved type.
The ion source structure has a porous gate structure, and therefore, the porous ion emitter has a wider and larger ion beam current than the earlier single-hole ion emitter. It uses a heating wire as the cathode and a wide beam ion source with a gate.
A separate ion source ca be added beside the evaporation source or the sputtering source,. The evaporation source can be a thermal evaporation source, an electron gun evaporation source or other evaporation source. The sputtering source can be a magnetron sputtering or ion beam assisted deposition.
Ion-beam Assisted Deposition (IAD) has many advantages. If the kinetic energy is insufficient during the deposition process, the film is not dense and has many voids. Heating bake or IAD can make the film dense.
The improvement of membrane quality by IAD includes four points:
- Thin film spectral stability
- Reduced water absorption
- Increased refractive index
- Roughness reduction
The energy (voltage and current) of the ion source should not be too large. If the deep impact of the growth film or the ionic gas (such as argon) is trapped in the film, the refractive index of the film will decrease and the uniformity will change.