High-power impulse magnetron sputter deposition for enhanced optical transmittance and electrical conductivity of flexible coating

Abstract

A transparent conductive material, mostly transparent conductive oxide (TCO), is essential and indispensable for flexible electronics. Different from the conventional, single-layered TCO, multilayered oxide/metal/oxide (OMO) structures have been investigated as a promising alternative. The metal layer serves to reduce the electrical resistance of the oxides and the transparency is enhanced by suppressing the reflection from middle metal layer and substrate. Meanwhile, due to the limited temperature tolerance of the flexible polymeric substances, high-power impulse magnetron sputtering technique has been used to deposit the OMO structures at a substrate temperature lower than 70 °C. Two different OMO multilayered structures, including ZnO/Ag/ZnO and ZnO/Cu/ZnO, are deposited on polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), and soda lime glass. The effects of layer thickness and metal type on the transmission and resistivity of the obtained OMO structures are investigated. The correlation between OMO structure characteristics and the resulting photoelectric properties are also studied. A 35-nm ZnO/20-nm Ag/30-nm ZnO having excellent resistivity of 6.2 × 10−5 Ωcm (7.2 Ωsq−1) and transmittance of 87.7% is demonstrated. Furthermore, after 3000 bending cycles, the multilayered OMOs on PET and PEN retain their superior electrical properties, exhibiting resistivity of 3.8 × 10−4 and 1.3 × 10−4 Ωcm, respectively.