Excimer laser synthesis of thin AlN coatings

A new technique for the production of thin AlN films on Al samples by direct laser synthesis is reported. This has the advantages of good adhesion, low temperature deposition and localisation. A metallic, pure Al sample is irradiated by an excimer laser under a nitrogen containing atmosphere at high intensity levels such that a plasma is formed above the sample. The active nitrogen atoms and ions contained in this plasma react with the hot melted Al surface resulting in the synthesis of an AlN layer. The influence of the incident laser fluence, nature and pressure of the ambient atmosphere and of the number of laser pulses on the chemical composition and crystalline structure of the synthesised layers is reported. Under optimised conditions a few μm thick polycrystalline AlN layer, containing only a few percent oxygen and exhibiting high hardness and very good adhesion, has been prepared on Al.