School of Electrical Engineering , KAIST , Daejeon 34141 , Republic of Korea.
ACS Appl Mater Interfaces. 2018 May 9;10(18):15829-15840. doi: 10.1021/acsami.8b01438. Epub 2018 Apr 30.
The lack of reliable, transparent, and flexible electrodes and insulators for applications in thin-film transistors (TFTs) makes it difficult to commercialize transparent, flexible TFTs (TF-TFTs). More specifically, conventional high process temperatures and the brittleness of these elements have been hurdles in developing flexible substrates vulnerable to heat. Here, we propose electrode and insulator fabrication techniques considering process temperature, transmittance, flexibility, and environmental stability. A transparent and flexible indium tin oxide (ITO)/Ag/ITO (IAI) electrode and an AlO/MgO (AM)-laminated insulator were optimized at the low temperature of 70 °C for the fabrication of TF-TFTs on a polyethylene terephthalate (PET) substrate. The optimized IAI electrode with a sheet resistance of 7 Ω/sq exhibited the luminous transmittance of 85.17% and maintained its electrical conductivity after exposure to damp heat conditions because of an environmentally stable ITO capping layer. In addition, the electrical conductivity of IAI was maintained after 10 000 bending cycles with a tensile strain of 3% because of the ductile Ag film. In the metal/insulator/metal structure, the insulating and mechanical properties of the optimized AM-laminated film deposited at 70 °C were significantly improved because of the highly dense nanolaminate system, compared to those of the AlO film deposited at 70 °C. In addition, the amorphous indium-gallium-zinc oxide (a-IGZO) was used as the active channel for TF-TFTs because of its excellent chemical stability. In the environmental stability test, the ITO, a-IGZO, and AM-laminated films showed the excellent environmental stability. Therefore, our IGZO-based TFT with IAI electrodes and the 70 °C AM-laminated insulator was fabricated to evaluate robustness, transparency, flexibility, and process temperature, resulting in transfer characteristics comparable to those of an IGZO-based TFT with a 150 °C AlO insulator.
用于薄膜晶体管 (TFT) 的可靠、透明和灵活的电极和绝缘体的缺乏使得透明、灵活的 TFT (TF-TFT) 难以商业化。更具体地说，传统的高工艺温度和这些元件的脆性一直是开发对热敏感的灵活衬底的障碍。在这里，我们提出了考虑工艺温度、透光率、灵活性和环境稳定性的电极和绝缘体制造技术。在 PET 基板上制造 TF-TFT 时，在 70°C 的低温下优化了透明且灵活的铟锡氧化物 (ITO)/Ag/ITO (IAI) 电极和 AlO/MgO (AM)-层压绝缘体。优化后的 IAI 电极的方阻为 7 Ω/sq，在暴露于湿热条件下仍保持其电导率，因为具有环境稳定的 ITO 覆盖层，其透光率为 85.17%。此外，由于延展性 Ag 膜，IAI 的电导率在经受 10,000 次 3%拉伸应变的弯曲循环后得以保持。在金属/绝缘体/金属结构中，与沉积在 70°C 的 AlO 膜相比，沉积在 70°C 的优化 AM 层压膜具有更高密度的纳米层压系统，因此其绝缘和机械性能得到了显著改善。此外，由于其优异的化学稳定性，使用非晶铟镓锌氧化物 (a-IGZO) 作为 TF-TFT 的有源通道。在环境稳定性测试中，ITO、a-IGZO 和 AM 层压膜表现出优异的环境稳定性。因此，我们使用 IAI 电极和 70°C AM 层压绝缘体制造了基于 IGZO 的 TFT，以评估其鲁棒性、透明度、灵活性和工艺温度，结果表明其转移特性可与具有 150°C AlO 绝缘体的基于 IGZO 的 TFT 相媲美。
