The ever-increasing demand for information storage has pushed research and development of nonvolatile memories, particularly magnetic disk drives and silicon-based memories, to areal densities where bit sizes are approaching nanometer dimensions. At this level, material and device phenomena make further scaling increasingly difficult. The difficulties are illustrated in the examples of magnetic media and flash memory, such as thermal instability of sub-100-nm bits in magnetic memory and charge retention in flash memory, and solutions are discussed in the form of patterned media and crosspoint memories. The materials-based difficulties are replaced by nanofabrication challenges, requiring the introduction of new techniques such as nanoimprinting lithography for cost-effective manufacturing and self-assembly for fabrication on the sub-25-nm scale. Articles in this issue describe block-copolymer lithographic fabrication of patterned media, materials studies on the scaling limits of phase-change-based crosspoint memories, nanoscale fabrication using imprint lithography, and biologically inspired protein-based memory.

Patterned magnetic recording media, in which data bits are stored in discrete single-domain magnetic particles, have been proposed for the next generation of recording media. To achieve high densities, features with periodicities on the order of 25 nm and below are required over large areas, which is a challenging task for any lithography process. Block copolymers (BCPs), which phase-separate into ordered periodic nanoscale structures, might provide a path to accomplish such patterning. In this article, we describe BCP lithography and show how the self-assembled patterns can be templated to make large-area arrays of nanoscale structures with long-range order.

Phase-change random-access memory (PCRAM) is a promising technology for future nonvolatile storage with the added potential for possible impact on dynamic random-access memory technologies. To be successful, however, PCRAM must be able to scale to dimensions on the order of a few tens of nanometers, considering the increasingly tiny memory cells that are projected for future technology nodes. The experiments discussed in this article directly address these scaling properties, examining both the materials themselves and the operation of nanoscale devices. One series of experiments is time-resolved x-ray diffraction studies of ultrathin films and nanostructures. Electron-beam lithography was applied to pattern thin films into nanostructures with dimensions down to 20 nm. The article also includes descriptions of prototype PCRAM devices, successfully fabricated and tested down to phase-change material cross sections of 3 nm × 20 nm. The measurements provide a clear demonstration of the excellent scaling potential offered by this technology.

Imprint lithography has a remarkable patterning resolution of less than 5 nm, and it is simultaneously capable of patterning over large areas with long-range order. This combination enables a broad range of potential applications including terabit-density magnetic storage, CMOS integrated circuits, and nanowire molecular memory. This article provides a review of the status of imprint lithography for nanoscale manufacturing. First, representative nanoscale devices and their manufacturing requirements are reviewed, along with key patterning challenges that have to be overcome to enable these nanoscale applications. Two classes of top–down nanopatterning techniques, namely, photon-based lithography and proximity mechanical nanopatterning (including imprint lithography), are described, followed by the three primary building blocks of imprint lithography: imprint masks, tools, and materials. Theresults of the lithography process are detailed in terms of process data such as long-range order in the placement and size of the nanostructures, process throughput, and overall cost considerations.

The concept of optical protein-based memory has been of interest since the early 1970s. Yet, no commercially available protein-based memory devices exist. This review presents an analysis of the main challenges associated with the practical implementation of such devices. In addition, the discussion includes details on the potential of using the unparalleled properties of photochromic proteins by creating an optical data storage disk drive with unmatched features and, particularly, record-high data densities and rates.