Coatings

Functional thin films can be produced in many ways. Most commonly used are:

1. Thermal evaporation
2. Ion sputtering
3. Chemical vapor deposition

Large areas are difficult to coat economically due to expensive vacuum chambers. Large chambers lower the heat radiation to substrates from evaporation sources or sputtering targets but still cause a problem for heat sensitive materials like plastics. Chemical vapor deposition does not necessarily need large vacuum chambers but chemical reaction normally requires temperatures of several hundreds of degrees Celsius. Optimization of flow geometry and substrate rotation is often required to achieve homogeneous film thickness over a large area.

The ideal film deposition method would turn all input energy directly to kinetic energy of deposited material thus minimizing the heat radiation and conduction away from the target. The ideal film deposition method would also selectively detach atoms from areas of the target that optimize the film thickness homogeneity at the substrate. Finally the quality of the film and adhesion to the substrate are key problems that require process optimization. The ideal deposition method should enable independent parameter control of the substrate temperature, stochiometry / size control of deposited "particles" and finally the control of kinetic energy of the flux impinging the substrate.

Laser ablation and deposition has long been studied as an ideal method for producing thin films. Ultra short pulsed laser deposition (USPLD) is shown to fulfill most of the requirements for the ideal film deposition method. The lack of a compact industrial scale laser source has so far prevented the breakthrough of USPLD.