Monitoring the Evolution of Molecular Structure in Transistors by Interfacial Spectroscopy

Technical Description: This project uses interface-specific vibrational sum frequency generation spectroscopy to study molecular vibrations and their orientations at the active interface in organic field-effect transistors. An underlying mission of this work is to spectroscopically monitor the evolution of the interface in operational devices to gain insight into the relationships between interfacial molecular structure and function. The activities establish the role of casting solvents and interfacial dipoles at the dielectric interface in enhancing the electrical performance of thin film transistors. The project also explores the use of zirconium phosphonate self-assembled nanodielectrics on the interfacial organic structure. In addition, the research team uses multiplexed sum frequency spectroscopy to measure the temporal evolution of molecular structures and carrier accumulation in the dielectric and organic semiconductor layers during thermal annealing. The in-situ-nature of these experiments provides a new perspective on the materials response from inside the functioning device, with the potential to describe not only what changes, but also what the timescales of structural change are and how these properties relate back to the macroscopic electrical response.

Non-Technical Description: Transistors are one of the basic building blocks of every digital device, from cell phones to grocery store check-out scanners. During operation, electricity moves along an interface and the arrangement of atoms or molecules in this region determines how efficiently the charges can flow. This project uses specialized optical measurements to determine how the molecules in these devices are ordered at the microscopic level, and how they respond to the chemistry of the underlying surfaces and to thermal processing treatments. The project is interdisciplinary, producing next-generation scientists who are skilled in materials processing, and electrical and optical characterization techniques. In addition, the research team organizes and directs a three-day-long rural outreach event each summer as a part of the University on the Prairie program where they use hands-on demonstrations to make connections between the materials properties observed by the junior high school aged participants and the real-world technologies with which they are familiar.