Substrate pretreatment for improvements in structural and mechanical properties of zinc oxide coatings on glass

Abstract

Reactively sputtered zinc oxide coatings were deposited onto float glass substrates following exposure of the substrates to an oxygen ion beam. A Hall-effect linear ion source was used to produce ion beams at different nominal beam voltages in the range 0–1500 V, within an otherwise standard unbalanced magnetron sputtering system. Coatings were deposited onto the pretreated glass under identical operating conditions and were then characterised in terms of their structural and mechanical properties. A series of consistent trends were found revealing improvements in these properties with increasing ion beam voltage. For example, a reduction in the surface roughness of the deposited film, as measured via atomic force microscopy (AFM), was observed. Critical load scratch testing and mechanical wear testing demonstrated significant improvements in mechanical durability, with peak values occurring for glass that had been pretreated with a beam voltage of 1000 V. These improvements in structural and mechanical properties were obtained without any effect on the optical properties of these coatings, which were measured via spectrophotometry. X-ray diffraction analysis of these coatings indicated that they all had a strong (002) texture, but that the position and width of this peak varied with substrate pretreatment. This work demonstrates the ability to improve film properties through the pretreatment of substrates with the linear ion source.