Improvement of indium–tin oxide films on polyethylene terephthalate substrates using hot-wire surface treatment

Indium–tin oxide (ITO) thin films have been studied extensively in flat panel displays because they combine unique transparent and conducting properties. A continuous roll-to-roll sputter system was used to deposit ITO/SiO2 thin films on polyethylene terephthalate (PET) substrates with no intentional heating. Typical transmittance and resistivity of the ITO/SiO2/PET sample were 78% (400∼700 nm) and 7.5 × 10− 3 Ω cm, respectively. Changes in the characteristics of ITO/SiO2/PET after hot-wire surface treatment in oxygen were examined in terms of resistivity, transmittance, surface roughness and bond configuration. The effects of process parameters like iridium wire temperature, chamber pressure and process duration on the properties of the ITO films are studied in details and compared with the works by plasma or furnace annealing. Under optimum conditions, the resistivity of the ITO/SiO2/PET sample can achieve a minimum value of 1 × 10− 3 Ω cm with a transmittance of 82%. These results indicate that the hot-wire system can be utilized to realize better quality film and to overcome the technological limits imposed by the role-to-role sputtering conditions.