Flexible Electronics with PVDF-TrFE Based Ferro- and Piezo-Electric Materials

Date(s):

Location:
Jacobs Hall, Room 2512, Jacobs School of Engineering, 9500 Gilman Dr, La Jolla, San Diego, California 92093

Sponsored By:
Professor Tina Ng

Speaker(s):
Depak Saboo
Dept. of Materials Science and Engineering Indian Institute of Technology
National Center for Flexible Electronics
Indian Institute of Technology
Photo

Abstract:

Ferroelectric polymers such as poly (vinylidenedifluoride–trifluoroethylene) P(VDF-TrFE) are great alternative to conventional ceramics based non-volatile memory (NVM) devices owing to their low temperature and easy processing, compatible with flexible electronics. We have shown that the ferroelectric properties, in particular coercivity, can be dramatically improved by suitably controlling the microstructure of P(VDF-TrFE) thin films through manipulating the cooling rate of the samples after annealing between Tc and Tm. Simultaneously, for reduction of electrical leakage in the P(VDF-TrFE) devices we incorporated of poly(methyl-methacrylate) (PMMA) with ferroelectric P(VDF-TrFE) in different configurations, specifically blend of the two polymers and their bilayer stack forms and analyzed evolution of the electrical properties, in particular ferroelectric response vis-à-vis morphological changes. In addition, the presentation discusses electrical and mechanical reliability of the P(VDF-TrFE) based capacitors on flexible substrate. We also evolved a co-solvent approach to processing P(VDF-TrFE) films. The results showed that single solvents with large dipole moment yield larger polarization at lower voltages and a much improved electrical fatigue behaviour, especially when the substrates are UV ozone treated. But with co-solvents, sspecifically, at DMSO:MEK ratio of 1:1, the co-solvent derived memory devices yield a high remnant polarization (~ 8.5 µC/cm2) at low coercive field (0.52 MV/cm) along with improved piezoelectric properties, perhaps with best d33 coefficient, in excess of 60 pm/V reported thus far. Most importantly, the fatigue endurance of these cosolvent derived ferroelectric films shows a dramatic improvement with no fatigue observed until 108 cycles making them attractive for device applications. The devices were stable up to 390K.

Speaker Bio:
Professor Deepak Saboo obtained his B. Tech. degree in Metallurgical Engineering from
the Indian Institute of Technology, Kanpur, in 1987. The graduate studies were completed in
Materials Science and Engineering, with a M.S. in 1989 from the University of Florida,
Gainesville, Florida (USA) and Ph. D. in 1993 from the University of California, Berkeley,
California (USA). Following the graduate studies, he conducted a year-long Post-Doctoral work
at the Argonne National Laboratory, Illinois (USA) and then another three years, beginning
1994, were spent in semiconductor device manufacturing and design at the Semiconductor
Products Sector of Motorola Inc., Phoenix, Arizona (USA). Deepak joined IIT Kanpur at the
end of 1997 as an Assistant Professor in the department of Materials Science and Engineering,
where he works to this date. Research interests of Deepak are in large area flexible
electronics. Specifically, he researches organic light emitting diodes, thin film transistors and
ferroelectric memories on flexible substrates.

Contact:
Cheryle Wills
Tel: 858-534-2498
email: clwills@eng.ucsd.edu