High Density Data Storage

The following sections are included:

• PREFACE

• CONTENTS

Areal density in magnetic data storage can be increased by the scaling method. However, the increase cannot continue indefinitely, due to the limit of fabrication technology and thermal stability. To postpone the onset of thermal instability, materials with high magnetic anisotropy are required for recording media in conventional longitudinal magnetic data storage. Nevertheless, this method is limited in further increasing the recording density because it requires extremely huge write field for high anisotropy media. Therefore, to achieve ultrahigh density magnetic data storage, alternative methods has to be explored. This chapter highlights recent advanced technologies and research work proposed for ultrahigh density magnetic data storage, including perpendicular recording, patterned media storage, self-assembling media and molecule-based magnets.

In past decades, optical data storage has undergone great developments, both technically and commercially. However, pushed by the urgent demands for a much higher storage density and a faster data process rate, we still need to put a great deal of effort into exploring new storage media and data process methods so as to overcome the current physical limits on optical data storage devices. So far, among various materials, photochromic compounds are regarded as the promising one, which can be manipulated in all photon modes and processed at the molecular scale with response times ultimately within nano- or pico-second levels. In the technical aspects, the main goals are to overcome the diffraction limit on 2D storage by near-field recording and to take advantage of volumetric storage by adding the third dimension.

As a promising approach to future large-capacity memories, electrical data storage has been receiving increased attention. Scanning probe microscopy-based recording technique has been demonstrated to be powerful for conducting data storage at nanometer scale or molecular scale. To improve the writing/reading speed, parallel recording techniques were further developed. In recent years, organic materials have been considered as promising recording media because of their low cost, simplicity, good stimuli–responsive properties and versatility in molecular design. To successfully implement organic materials into practical electrical recording, it still needs much more efforts to rationally design materials fulfilling more strict requirements including good film-forming property, stable reading-out, high on–off ratio, fast transition time, low power consumption, ease of fabrication etc. This chapter highlights the recent progress on electrical bistable materials and recording technologies for high-density electrical data storage, with emphasis on the motivation and the design of new materials and their recording mechanisms. The very recent multi-mode and spin-based recording techniques and realated materials are also discussed.

This chapter reviews the development of nanoscale data storage, i.e., “nanostorage.” As a new storage system, the recording mechanisms of nanostorage may be completely different to those of the traditional devices. Currently, two types of materials are being studied for potential application in nanostorage. One is molecular electronic elements, including molecular wires, rectifiers, switches and transistors. The other approach employs nanostructured materials such as nanotubes, nanowires and nanoparticles. The challenges for nanostorage are not only the materials, ultrahigh data densities, fabrication costs, device operating temperatures and large scale integration, but also the development of the physical principles and models. There are already some breakthroughs in this field, but it is still unclear what kind of nanostorage systems can ultimately replace the current silicon-based transistors. A promising candidate may be a molecular-nanostructure hybrid device with sub-10 nm dimensions.

The following sections are included:

• INDEX