Basic Study on High-density Ferroelectric Data Storage Using Scanning Nonlinear Dielectric Microscopy
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Basic Study on High-density Ferroelectric Data Storage Using Scanning Nonlinear Dielectric Microscopy Yoshiomi Hiranaga1, Kenjiro Fujimoto1, Yasuo Wagatsuma1, Yasuo Cho1, Atsushi Onoe2, Kazuya Terabe3 and Kenji Kitamura3 1 Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan 2 Pioneer Corporation, 6-1-1 Fujimi, Tsurugashima, Saitama, 350-2288, Japan 3 Nanomaterials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan ABSTRACT Scanning Nonlinear Dielectric Microscopy (SNDM) is the method for observing ferroelectric polarization distribution, and now, its resolution has become to the sub-nanometer order, which is much higher than other scanning probe microscopy (SPM) methods for the same purpose. Up to now, we have studied high-density ferroelectric data storage using this microscopy. In this study, we have conducted fundamental experiments of nano-sized inverted domain formation in LiTaO3 single, and successfully formed inverted dot array with the density of 1.5 Tbit/inch2. INTRODUCTION With the advance of information processing technology, the importance of high-density data storage is increasing. Studies on thermal fluctuation predicts that the magnetic storage, which plays a main role in this field, will reach a theoretical limit in the near future, and a novel high-density storage method is required. So, we have studied the application of ferroelectric materials to high-density storage media. Ferroelectrics can hold bit information in the form of a polarization direction. Moreover, the domain wall of typical ferroelectric material is as thin as the order of a few lattices [1]. This feature is favorable for high-density data storage. Recently, there are many reports on inverted domain formation in ferroelectric thin film using scanning probe microscopy (SPM). In this technique, inverted domain dots are formed by applying a relatively large voltage to the probe. These dots can be detected by piezoelectric imaging technique. Up to now, 6 Gbit/cm2 (39Gbit/inch2) artificial domain dot array formed in lead zirconate titanate (PZT) thin film has been reported [2]. However, in order to achieve the
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recording density of Tbit/inch2 order, improving the resolution of the domain detection device and the physical properties of the ferroelectric medium are required. The present authors have recently developed and reported scanning nonlinear dielectric microscopy (SNDM) for observing ferroelectric polarization distribution [3-5]. The resolution of this microscopy is sub-nanometer order [4], which is much higher than other scanning probe microscopy (SPM) methods for observing polarization distribution [6]. So SNDM is considered to be a powerful tool for ferroelectric domain engineering. Moreover, SNDM is promising for a pickup head of a ferroelectric high-density storage system, because this method is purely electrical, and therefore high-speed data transfer can be realized using this method. On the other hand, i
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