www.afm-journal.de FULL PAPER © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 3124 www.MaterialsViews.com wileyonlinelibrary.com Xiang-Zhong Chen, Qian Li, Xin Chen, Xu Guo, Hai-Xiong Ge, Yun Liu, and Qun-Dong Shen* 1. Introduction With the development of modern electronics, more and more organic electronic devices, such as flexible display screens and disposable radio-frequency identification (RFID) tags, come into view. The tendency of these electronic devices is miniaturi- zation, high portability, and low-power consuming. It requires the key components, i.e., memory parts, to satisfy high density storage, low volume, light weight, fast switching speed, and long- term stability. To fulfill different needs of data storage, dynamic random access memory (DRAM), hard-disk drives (HDD), and flash memory have been used. Nevertheless, neither of them is suitable for the newly developed devices because DRAM needs refresh cycles (and thus extra power supply), HDD is too slow to access and power-consuming, and the flash has limited endurance. [1] Fer- roelectric thin-film memories have been fabricated onto standard silicon integrated circuits, and take the advantages of fast switching, low power consumption, and long durability over competing nonvolatile memories. [2] Most of the ferroelectrics cur- rently in use are inorganic materials with complex structures, which make them easily damaged in the existing lithographic process. [3] The inorganic materials are also brittle and generally fracture at low strain, and thereby are not fully compatible with the state-of-art flexible organic electronics. As canonical organic ferroelectric mate- rials, poly(vinylidene fluoride) (PVDF) and its copolymers, have been extensively studied for high-k composites, [4–6] electrome- chanical actuators, [7] ultrahigh energy density capacitors, [8,9] and on-chip cooling devices. [10] Vinylidene fluoride-trifluoroethylene copolymers, i.e., P(VDF-TrFE)s, have remnant polarization as high as 10 μC cm -2 , [11] and show promise as materials for thin-film and non-volatile memories. Moreover, the excellent solubility, processibility, and flexibility facilitate the integration of the copolymers in electronic devices. P(VDF-TrFE)s require relatively large electric field ( ≈50 MV m -1 ), usually an order of magnitude higher than those of inorganic materials, to switch the spontaneous polarization in the crystals. [11] By scaling down the film thickness to the submicrometer scale, the ferroelec- tric polymer memories can store data by applying bias of a few volts, which comply with the requirements of integrated circuit. Recent experimental results demonstrate that ferroelectricity persists in the copolymer thin films with thickness down to a few molecular monolayers. [12] To achieve ultrahigh density information storage, atomic force microscopy (AFM) has been extensively used for nano- scopic write operations on continuous ferroelectric films, where the polarization of ferroelectric domains can be switched by applying a voltage between a metallic AFM tip and the bottom electrode. [13] Such nanoscale writing could produce an array of ferroelectric domains at a density of tens of gigabytes per square inch, and allow creating complicated patterns under computer control of tip motion. However, direct polarizing by the AFM tip has some drawbacks such as domain merging or collapsing due to large local field, and cross-talk where the Nano-Imprinted Ferroelectric Polymer Nanodot Arrays for High Density Data Storage Ferroelectric vinylidene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] free-standing ultrahigh density ( ≈75 Gb inch -2 ) nanodot arrays are success- fully fabricated through a facile, high-throughput, and cost-effective nano- imprinting method using disposable anodic aluminum oxide with orderly arranged nanometer-scale pores as molds. The nanodots show a large-area smooth surface morphology, and the piezoresponse in each nanodot is strong and uniform. The preferred orientation of the copolymer chains in the nanodot arrays is favorable for polarization switching of single nanodots. The ferroelectric polymer memory prototype can be operated by a few volts with high writing/erasing speed, which comply with the requirements of integrated circuit. This approach provides a way of directly writing nanometer electronic features in two dimensions by piezoresponse force microscopy probe based technology, which is attractive for high density data storage. DOI: 10.1002/adfm.201203042 X. Z. Chen, X. Chen, Prof. Q. D. Shen Department of Polymer Science & Engineering and Key Laboratory of Mesoscopic Chemistry of MOE School of Chemistry & Chemical Engineering Nanjing University Nanjing, 210093, China E-mail: qdshen@nju.edu.cn Q. Li, Prof. Y. Liu Research School of Chemistry Australian National University ACT 0200, Australia X. Guo, Prof. H. X. Ge Department of Materials Science & Engineering and National Laboratory of Solid State Microstructures Nanjing University Nanjing, 210093, China Adv. Funct. Mater. 2013, 23, 3124–3129