Effect of Low Nitrogen Concentration on Reactive RF Sputtering of Boron

Monolayer boron and B/Mo/B/Mo coatings were prepared by reactive magnetron sputtering in the N2/Ar atmosphere with different RF powers, and the effect of the N2:Ar flow ratio was studied. It was found that as the N2:Ar flow ratio increased, the deposition rate of boron coatings exhibited three different stages of variation due to different mechanisms. The variation of deposition rate with increasing N2:Ar flow ratio was consistent for different RF powers. Berg's model explained experimental findings. XPS revealed that the coatings contained more than 86 % boron nitride (BN) when the N2 flow ratio was above 0.053 at 300W RF power. An optimal ratio exists that maximizes the boron deposition rate and produces a nearly pure boron nitride coating without target poisoning.