Characterization of Sn-doped In₂O₃Film on Roll-to-Roll Flexible Plastic Substrate Prepared by DC Magnetron Sputtering

Abstract

Electrical and crystallographic properties of Sn-doped In2O3 (ITO) films prepared on polyethylene terephthalate (PET) webs as the roll-to-roll flexible substrates by DC magnetron sputtering were examined before and after the annealing under air. The ITO films were deposited at the substrate temperature of 100°C under several O2/Ar ratios in the range between 0 to 0.42. Before the deposition, repeated passing of the PET web over the heated drum in the vacuum chamber, i.e. degassing process, was carried out to control the contained H2O molecules in the PET substrate. When the number of degassing repetitions was insufficient, the deposited ITO films were more affected by H2O because more H2O remained in the substrate. In the case of insufficient degassing, crystallization of the ITO films by the annealing was suppressed, and the ionization of Sn atoms into donors was prevented. Such properties caused by insufficient degassing were estimated to be due to termination of the In–O network with the –OH radicals. On the other hand, the ITO films deposited on sufficiently degassed PET substrate were well crystallized and Sn atoms were well ionized.