Textured organic ferroelectric-based transistors as neuromorphic devices

Synapses and neurons are the fundamental information processing units of the human brain. Mimicking the human brain provides a vast platform for the development of energy-efficient neuromorphic computers, which could solve complex problems faster than today’s computers with very low energy consumption. This project supports research and educational activities for developing high performing transistors based on organic semiconductors and applying them in artificial synaptic devices. Organic semiconductors are extremely versatile for absorbing wavelengths from the ultraviolet to the near infrared and combining them with ferroelectric dielectrics in transistor architecture allows for both electrical and photonic synapses to emulate important functions of biological synapses. The project involves both fundamental and applied research by bringing together a team with expertise in device physics, engineering, materials, and biophysics. A broad range of students will be trained during the project, which involves conducting hands-on projects on electronics and nanopore experiments for high school students. A new biophysics experiment will be developed as part of the Advanced Laboratory, where undergraduate students will be exposed to a Nobel Prize winning single-molecule methodology that was instrumental in uncovering activities underlying neuron function. The scientific objective of the project is to develop organic ferroelectric transistor based neuromorphic devices. Combined with polymer ferroelectric dielectrics, organic field-effect transistors (FETs) are promising candidates for both electrical and photonic synapses to emulate important functions of biological synapses. The project takes an integrated approach of developing new architectures for manipulating the ferroelectric phase including the concept of negative capacitance for lowering the subthreshold swing and operating voltage in organic ferroelectric FETs, using novel lithography techniques for patterning and barrier modification of the metal contacts, and investigating both electrical and photonic synapses. Thus far, FET based photonic synapses have mainly relied on oxide semiconductors, which are less versatile in terms of tunable bandgap energies. Along with the range of suitable bandgap energies and effective exciton dissociation mechanisms in organic semiconductors, texture-poled ferroelectric dielectrics in organic FET architectures are promising for increasing the dynamic range for neuromorphic computing. The relaxation characteristics of organic semiconductors may be controlled by the polarization state of the ferroelectric dielectric. Furthermore, the potential of negative capacitance organic FETs opens an exciting avenue for low energy consumption neuromorphic devices. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.