Development of Ferroelectric Data Storage Test System for High-Density and High-Speed Read/Write
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Development of Ferroelectric Data Storage Test System for High-Density and High-Speed Read/Write Yoshiomi Hiranaga1, Kenkou Tanaka1, Tomoya Uda1, Yuichi Kurihashi1, Yasuhiro Kimoto1, Hikari Tochishita2, Michio Kadota2 and Yasuo Cho1 1 Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan 2 Murata Manufacturing Co., Ltd., 2288 Oshinohara, Yasu-shi, Shiga, 520-2393, Japan ABSTRACT In this study, we have developed ferroelectric data storage test systems based on scanning nonlinear dielectric microscopy (SNDM) to conduct various experiments concerning read/write capability. Nanodomain formation on ferroelectric recording media was studied using the data storage test system. A nanodomain dot array was successfully written on a single-crystal LiTaO3 recording medium. The diameter of the written dot was as small as 7 nm. Epitaxial-thin-film LiTaO3 recording media were also developed. Nanodomain dots with the diameter of 25 nm were written on the thin-film recording medium. In addition, a non-contact probe-height control technique was adopted to solve the problem of tip abrasion using higher-order nonlinear dielectric response detection method. Finally, a hard-disk-drive (HDD)-type ferroelectric data storage test system was developed for conducting read/write tests under conditions close to those of actual operation. Capabilities of reading at the bit rate of 2 Mbps and writing at the bit rate of 20 Mbps were confirmed using the HDD-type data storage test system. INTRODUCTION There is growing interest in probe data storage technology to realize ultrahigh recording densities of over 1 Tbit/inch2 [1,2]. In particular, probe data storage using ferroelectric materials as recording media is one of the most promising methods, because artificial nanosized domains with high stability can be formed on ferroelectric materials [3,4]. On the other hand, several techniques have been proposed for distinguishing the polarities of ferroelectrics [5,6]. Scanning nonlinear dielectric microscopy (SNDM) is one of the most powerful tools for observing the domain structures of ferroelectrics [7]. The resolution of SNDM has reached sub-nanometer scale. Additionally, SNDM can detect the polarization direction signal at high speed because it is purely electrical way. Therefore we have developed the ferroelectric data storage test system based on SNDM aiming at realization of high-density and high-speed recording. This paper summarizes the recent experimental results concerning ferroelectric high density data storage. EXPERIMENT Several experiments concerning nanodomain formation on ferroelectrics were carried out using the ferroelectric data storage test system based on SNDM. A Schematic diagram of the system is shown in figure1. The read/write (R/W) head is composed of a sharp-pointed conductive probe and an oscillator. When the data written on a ferroelectric recording medium is read, the polarization directions of the data bits are detected as nonlinear dielectric respons
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