Flexible W-doped In2O3 films grown on ion beam treated polyethylene terephthalate substrate using roll to roll sputtering

We investigated the effect of Ar ion beam treatment on a polyethylene terephthalate (PET) substrate to grow high-quality flexible W-doped In2O3 (IWO) films using a lab-scale roll-to-roll (RTR) sputtering system at room temperature. The electrical, optical, morphological, and mechanical properties of the flexible IWO films sputtered on the ion beam-treated PET and untreated PET substrates were comprehensively compared. In particular, the mechanical flexibility of the RTR sputtered IWO films was investigated in detail using custom-made bending, rolling, and twisting testers. Based on water contact angle and X-ray photoelectron spectroscopy (XPS) measurements, we found that the surface energy change and decreased C-O and CË­O groups on the PET substrate led to flexible IWO films with improved adhesion and better mechanical properties. In addition, we compared repeating cooling and heating cyclic stability of the flexible thin film heaters with RTR sputtered IWO films before and after ion beam treatment to show feasibility of ion beam treating process during RTR sputtering.