Deposition of abrasion resistant single films and antireflective coatings on sapphire

• We deposited a series of single films and antireflective coatings on sapphire.
• Nanohardness was investigated.
• Sand trickling and tightened oscillating abrasion test were performed.
• Very stable antireflective coating based on Si3N4 could be produced
• SiAlOx and SiZrOx is also a promising low index material.

A series of different oxide and nitride antireflective coatings as well as single films on sapphire substrates have been deposited by magnetron sputtering. The layer stacks consist of 5–7 individual layers with a total thickness of around 300 nm. Both high-index materials and low-index material were analyzed. The mechanical stability was investigated by means of optical haze increase during falling sand (“sand trickling test”) and by thickness loss during oscillating abrasion in a sand bath (tightened “Bayer test”). The dependence of the abrasion tests results on mechanical film properties, i.e. the nanoindentor hardness, was analyzed. No clear correlation of the Bayer test results and the sand trickling test results was found, which indicates that the abrasion mechanisms are different. A nitride based antireflective coating with excellent properties from both tests has been produced.