Deposition of indium tin oxide films on polycarbonate substrates by using ion beam processes

Abstract

Indium tin oxide (ITO) films have been deposited on polycarbonate (PC) substrates by an oxygen ion-assisted deposition (IAD), where the PC substrates were pretreated by an ion-assisted reaction (IAR) to increase a surface energy of PC surfaces resulting in improving adhesion between a film and a substrate. In the IAD process, an oxygen ion energy and an arrival ratio were varied from 60 to 500 eV and from 0.25 to 1.50, respectively. During the pretreatment using the IAR, the PC substrates were bombarded by Ar+ ions with the energy of 1000 eV in oxygen environment. After IAR treatment, the surface energy of the PC substrates increased largely due to a polar component related to a newly formed functional group, which is identified as carbonyl group by x-ray photoelectron spectroscopy analysis. The adhesion between the film and the substrate was estimated qualitatively by a peel test using Scotch tape™ and by a water boiling test, and the significant adhesion improvement was obtained in the ITO films deposited on the IAR treated PC substrates. The surface morphology and electrical resistivity of the ITO films were significantly dependent on the bombarded oxygen ion energy, the arrival ratio and the substrate temperature. The low electrical resistivity (4.1×10−4 Ω cm) and high transmittance (≈80%) in a visible range were obtained in the 60 eV ion-assisted films deposited at the arrival ratio of 1.00 and substrate temperature of 50 °C. Based on these results, an effect of ion bombardment on the material properties of the ITO film during film growth was discussed in detail and a mechanism of adhesion improvement for the ITO films deposited on the IAR treated PC substrates was briefly proposed.