PhD Thesis Colloquium: : Ms. Shivangi Srivastava (28/07/25)
Thesis title:
Overcoming Processing Constraints in Organic Electronics: Crosslinking Strategies and Ultra-Thin Film Integration
Faculty advisor(s):
Prof. Praveen C Ramamurthy
When?
28th July, 2025 (Monday), 3:00 PM (India Standard Time)
Where
KPA Auditorium, Dept of Materials Engineering
Abstract:
Silicon-based technologies have long dominated modern electronics due to their reliability, performance, and scalability. However, they fall short in applications requiring flexibility, biodegradability, and large-area integration. Organic Field-Effect Transistors (OFETs) offer a promising alternative, enabling solution-processable, low-temperature fabrication on flexible and biodegradable substrates. A key challenge in advancing OFET performance lies in the precise patterning of polymer semiconductor layers. Accurate patterning reduces crosstalk, lowers parasitic capacitance, and enhances device speed and scalability. However, traditional lithographic methods are often incompatible with organic materials like polymer semiconductors, which are sensitive to solvents and processing conditions. The complexity further increases when fabricating advanced architectures requiring additional layers such as electrodes, dielectrics, or encapsulants atop the polymer, without degrading its electronic properties.
To overcome these challenges, a direct electron beam-induced crosslinking (EBIC) method was developed for patterning P3HT without the need for resists. A range of characterisation techniques, Raman, PL, AFM, UPS, and KPFM, were employed to evaluate the effects of EBIC on material properties. Electrical characterisation of OFETs fabricated using EBIC-patterned P3HT across varying e-beam doses identified optimal conditions for balancing material preservation and performance enhancement. Additionally, successful top-layer lithography was demonstrated using an orthogonal resist, enabling fabrication of top-contact bottom-gate OFETs, with performance benchmarked against bottom-contact counterparts.
Complementing the patterning strategy, ultra-thin P3HT films with precise thickness control were fabricated via modulation of e-beam energy and dose. Ultra-thin films exhibit superior mechanical flexibility, transparency, and low contact resistance, making them ideal for next-generation flexible electronics. OFETs based on ultra-thin P3HT films showed high performance, and the viability of the patterning approach was further validated through the fabrication of a depletion load inverter circuit using both optical and e-beam lithography.