Advanced chemical science-based high-resolution low-cost printing for high performance printed electronics

• Main Author: Shi, Jingsheng
• Other Authors: Li Changming
• Format: Theses and Dissertations
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Materials::Microelectronics and semiconductor materials; DRNTU::Engineering::Nanotechnology
• Online Access: https://hdl.handle.net/10356/48060
• Institution: Nanyang Technological University

Printing processes are promising alternatives to photolithography for printed electronics. It is essential to applications such as large-area flat-panel displays, electronic paper, radio frequency identification tags (RFID tags), and ultraportable disposable sensors, which have requirements other than operating speeds and increasingly complicated circuits for better manufacturability. The impact of printing processes on device performance is still underexplored. Understanding and advancing the chemical sciences involved in printing electronics is essential to develop new printing technologies or improve existing printing processes for high performance organic semiconductor/CNT- based printed electronics. UV transfer embossing using selective cross-linking of resins has been improved for lower gate leakage current, and significant roughness reduction at the dielectric-semiconductor interface, leading to improved device performance. The resulting printed OTFT produced one order higher mobility (0.01 - 0.02 cm2/V s) and two orders higher on/off ratio (104) compared to top- gated devices. In-situ polymerization in PDMS-based nanocomposite dielectric material was used to replace cross-linking of UV resins and develop a low-cost adhesive-free direct transfer printing process. The adhesive-absent semiconductor-electrode interface showed width-normalized contact resistance of ~100 kΩ·cm. Further improved device performance with a high mobility of 0.038 cm2/V s and an on/off ratio of 104 - 105 was demonstrated. The first use of spatial control of oxygen-inhibition of photopolymerization in acrylate-based materials was demonstrated as a universal printing technique applicable on different substrates. The new approach eliminates the expensive equipment and materials in the conventional lithography process. This new printing method was also used to fabricate printed TFTs on Si and PET substrates, showing very good device performance. A single-step transfer printing method to fabricate CNT finFETs with novel PVA dielectric-wrapped CNT network was developed and the printed high performance CNT finFETs with mobility of 27 ± 10 cm2/V s and 102-104 on/off ratio were fabricated. The method is a versatile low-cost printing technology to mass-produce high performance all-printed CNT-based electronics on flexible large-area substrates for a broad range of electronic applications. In summary, advances in chemical science for new and improved printing processes were studied to offer better device performance for printed electronic and to address the technological issues in other printing processes while fundamental studies were conducted on how the printing processes would affect the performance of the printed devices from various aspects. This research offers chemical, material and mechanical engineering approaches for better manufacturability and high performance printed electronics, in addition to providing fundamental insights on the effect of the printing process on devices.