Polymeric gate dielectric interlayer of cross-linkable poly(styrene-r-methylmethacrylate) copolymer for ferroelectric PVDF-TrFE field effect transistor memory Jiyoun Chang a , Chang Hak Shin b , Youn Jung Park a , Seok Ju Kang a , Hee June Jeong a , Kap Jin Kim c , Craig J. Hawker d , Thomas P. Russell e , Du Yeol Ryu b , Cheolmin Park a, * a Department of Materials Science and Engineering, Yonsei University, Seoul, Republic of Korea b Department of Chemical Engineering, Yonsei University, Seoul, Republic of Korea c College of Engineering, Department of Advanced Polymer and Fiber Materials, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea d Material Research Laboratory and Departments of Materials, Chemistry and Biochemistry, University of California, Santa Barbara, CA 93016, USA e Department of Polymer Science & Engineering, University of Massachusetts, Amherst, MA 01003, USA article info Article history: Received 6 February 2009 Received in revised form 26 March 2009 Accepted 13 April 2009 Available online 21 April 2009 Keywords: PVDF-TrFE Transistor Non-volatile ferroelectric memory Gate leakage Organic insulator Cross-linkable poly(styrene-r- methylmethacrylate) copolymer abstract A new polymeric gate dielectric interlayer of a cross-linkable poly(styrene-random-meth- ylmethacrylate) copolymer is introduced with a good thermal and chemical resistance in bottom gate Ferroelectric Field Effect Transistor (FeFET) memory with pentacene active layer and ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) one. A thin uniform PVDF-TrFE film was successfully formed with well defined ferroelectric microdomains on an interlayer. Thickness of the interlayer turns out to be one of the most important factors for controlling gate leakage current which is supposed to be minimized for high ON/OFF bistability of a FeFET memory. An interlayer inserted between gate elec- trode and PVDF-TrFE layer significantly reduces gate leakage current, leading to source– drain OFF current of approximately 10 11 A in particular when its thickness becomes greater than approximately 25 nm. A reliable FeFET device shows a clockwise I-V hysteresis with drain current bistablility of 10 3 at ±40 V gate voltage. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction The recent demand for technologies in portable applica- tions which enable the rapid manipulation, caching, and storage of large amounts of data leads to great develop- ment of new types of non-volatile memory devices [1]. Furthermore, significant efforts have been devoted to establish non-volatile memories based on organic and polymer materials for last several years on account of their capability of solution-process, flexibility and resulting low cost fabrication [2,3]. Ferroelectric polymer memory is also one of the candidates in particular due to the additional benefit of compatibility with common organic electronic technologies [1,2]. The representative ferroelectric polymers such as poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene(TrFE) have received great attention be- cause of their ferroelectric properties originating from bistable permanent dipoles between hydrogen and fluo- rine atoms perpendicular to chain direction [4]. Particu- larly for non-volatile memory with a non-destructive readout capability and a smaller cell size, a memory struc- ture based on field effect transistor (FET) has been recently studied. Ferroelectric thin films are required as gate dielec- tric to form a Ferroelectric Field Effect Transistor (FeFET) device structure. The polarization state of the ferroelectric gate set by the polarity of the writing gate voltage controls 1566-1199/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.orgel.2009.04.005 * Corresponding author. Tel.: +82 2 2123 2833; fax: +82 2 312 5375. E-mail address: cmpark@yonsei.ac.kr (C. Park). Organic Electronics 10 (2009) 849–856 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel