Fabrication of All Printed Flexible Carbon Nanotube Transistor and its Application
With the demand of new electronic sensors and systems for sophisticated modern digital environment, it is highly required to investigate nontraditional electronic devices. For those flexible electronics offers low-cost, non-rigid, large area fabrication of electronic devices by various printing technologies. Among all printing technologies, aerosol jet printing offers precise, accurate printing of large numbers of materials with high resolution. However, printability of high mobility semiconducting channel and thin dielectric layer are some of the major roadblocks in the performance of completely printed flexible thin film transistors (TFT). The solution processed material that has shown promising results when compared with traditional semiconducting material is Carbon nanotube (CNT). Though there are some research works available on fabrication of CNT TFT, only few have achieved high performance in terms of minimum gate threshold voltage and high frequency operation. In this work, we propose aerosol jet printing of a flexible carbon nanotube based TFT with poly vinyl phenol (PVP) based crosslinked polymer as the dielectric material using a single printing technique. Previously, crosslinked PVP has been used as the dielectric material for organic transistors, where the materials are deposited using spin coating techniques. In this work, for the first time crosslinked PVP was deposited using aerosol jet printing. The ink properties and aerosol jet printer control parameters were investigated and optimized to deposit thin pinhole free dielectric layer. Flexible TFTs were printed using silver nanoparticles, CNT and the optimized crosslinked PVP ink and characterized for DC performance. The ratio of PVP and the crosslinking agent was optimized to lower hysteresis and gate leakage current. With the optimized ratio, very thin dielectric layer was printed to enable low gate threshold volage operation (4V) of flexible CNT-TFT. This is a significant progress towards the application of printed CNT TFT in low power electronic circuits. The printed devices were also used in analog circuits to verify their operations in frequency domain. The TFTs were used as an inverter and switch to obtain the maximum frequency signal that the device can pass. This ensures the applicability of completely printed CNT transistor.
flexible electronics, carbon nanotubes, polymer dielectrics, aerosol jet printing
Mishra, B. (2022). Fabrication of all printed flexible carbon nanotube transistor and its application (Unpublished dissertation). Texas State University, San Marcos, Texas.