Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation

This work reports on low temperature deposition of conducting indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150 °C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 × 10⁻⁴ Ω-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Ω/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.