Design and preparation of In₂O₃-based multi-layer functional films

Leveraging the conductivity of In₂O₃ and the wear resistance and anti-corrosion behaviour of SiO₂ and TiO₂, In₂O₃, In₂O₃/SiO₂ and In₂O₃/TiO₂ films were prepared via magnetron sputtering to meet the transparency, conductivity, wear resistance and corrosion resistance requirements for external screens of wearable devices. The films exhibited excellent sheet resistance of 13–28 Ω·sq⁻¹, which fully met the conductivity criteria. Owing to the light interference effect, the average transmittance of the In₂O₃ film (77%) was higher and lower than those of the In₂O₃/TiO₂ (69%) and In₂O₃/SiO₂ (83%) films, respectively. After soaking in sweat solutions for 48 h, the In₂O₃ and In₂O₃/SiO₂ films maintained their optical and electrical properties and the In₂O₃/TiO₂ film was partially peeled off in the acid solution. The low transmittance and corrosion resistance of the In₂O₃/TiO₂ film were due to severe oxygen deficiency in the TiO₂ layer, indicated by the certain amount of Ti₂O₃ and metal Ti in XPS. The wear failure time of the In₂O₃/SiO₂ film (42 h) was greater than those of the In₂O₃ (30 h) and In₂O₃/TiO₂ (24 h) films because of its hard SiO₂ top layer. Based on the ‘parallel sheet resistance principle’, the resistivity of the double-layer films was mainly attributed to the conductive In₂O₃ layers. The wear and corrosion resistances were ascribed to the top passive transparent layers, in which the SiO₂ layer showed its excellent optical and electrical performance stabilities before and after corrosion and wear resistance functions. With its commonly high transparency and conductivity as well as its high wear and corrosion resistances, the In₂O₃/SiO₂ film exhibits application potential for external screens of wearable devices.