Thin ferroelectric poly(vinylidene fluoride-chlorotrifluoro ethylene) films for thermal history independent non-volatile polymer memory

• Published in: Organic electronics Vol. 13; no. 3; pp. 491 - 497
• Main Authors: Kim, Richard Hahnkee, Kang, Seok Ju, Bae, Insung, Choi, Yeon Sik, Park, Youn Jung, Park, Cheolmin
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2012; Elsevier
• Subjects: Applied sciences; Crystal phase; Design. Technologies. Operation analysis. Testing; Dielectric, amorphous and glass solid devices; Electronics; Exact sciences and technology; Ferroelectric capacitor; Ferroelectric polymer; Integrated circuits; Integrated circuits by function (including memories and processors); Non-volatile polymer memory; Poly(vinylidene fluoride-chlorotrifluoro ethylene); Remnant polarization; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors; Remnant polarization; Crystal phase; Non-volatile polymer memory; Poly(vinylidene fluoride-chlorotrifluoro ethylene); Ferroelectric capacitor; Ferroelectric polymer; Annealing; Heat treatment; Ferroelectric properties; Crystalline material; Sphere; Field effect transistor; Hysteresis loop; Nanometer scale; Ferroelectric materials; Spherulites; Non volatile memory; Vinylidene fluoride polymer; Integrated circuit; Ethylene copolymer; Ferroelectric capacitors; Microstructure; Melting point; On off effect
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2011.11.018

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► We researched the ferroelectric properties of PVDF-CTFE in MFM capacitor and FeFET. ► α and β type crystals were developed, depending upon thermal processing history. ► Both types of crystals turned out ferroelectric in films. ► The reliable data retention properties were obtained in FeFET memory device.
In this study, we investigated the molecular and microstructures of thin poly(vinylidene fluoride-chlorotrifluoro ethylene) (PVDF-CTFE) copolymer films with three different CTFE compositions of 10, 15, 20wt% with respect to PVDF in relation with their ferroelectric properties. All PVDF-CTFE annealed at 130°C showed consecutive TTTT trans conformation with β type crystals while films molten and re-crystallized from a temperature above their melting points exhibited α type crystals with characteristic TGTG conformation. Microstructures of the films treated with the two different thermal histories also supported the formation of β and α type crystals with hundreds of nanometer scale sphere caps and micron level spherulites, respectively. Interestingly, PVDF-CTFE films with both α and β type crystals gave rise to relatively high remnant polarization of approximately 4μC/cm2 in metal/ferroelectric/metal capacitors regardless of the composition of CTFE. The ferroelectric polarization of a PVDF-CTFE film independent of thermal processing history allowed a wide processing window and easy fabrication protocol, resulting in a non-volatile ferroelectric field effect transistor memory which exhibited saturated hysteresis loops with the current ON/OFF ratio of approximately 103 at ±60V sweep and reliable data retention.