Ultra high density scanning electrical probe phase-change memory for archival storage

The potential for using probe-based phase-change memories for the future archival storage at densities of around 1 Tbit/in.² is investigated using a recording medium comprising a Si/TiN/DLC/GeSbTe/diamond-like carbon (DLC) stack together with a conductive PtSi tip for writing and reading. Both experimental and computational simulation results are presented. The simulations include a physically-realistic threshold switching model, as well as the effects of thermal boundary resistance and electrical contact resistance. The simulated bit size and shape correspond closely to that written experimentally

Force modulation for enhanced nanoscale electrical sensing

Scanning probe microscopy employing conductive probes is a powerful tool for the investigation and modification of electrical properties at the nanoscale. Application areas include semiconductor metrology, probe-based data storage and materials research. Conductive probes can also be used to emulate nanoscale electrical contacts. However, unreliable electrical contact and tip wear have severely hampered the widespread usage of conductive probes for these applications. In this paper we introduce a force modulation technique for enhanced nanoscale electrical sensing using conductive probes. This technique results in lower friction, reduced tip wear and enhanced electrical contact quality. Experimental results using phase-change material stacks and platinum silicide conductive probes clearly demonstrate the efficacy of the proposed technique. Furthermore, conductive-mode imaging experiments on specially prepared platinum/carbon samples are presented to demonstrate the widespread applicability of this technique

Ultra-high density scanning electrical probe phase-change memory for archival storage.

In our work, we investigate the recording and readout performance of such phase-change memories and demonstrate experimental and simulation results which are based on a particular medium stack (Si/TiN/DLC/GST/DLC). The recording is achieved by injecting electrical current from a conductive tip to the storage medium to cause phase transformation through Joule heating, while readout is realised by sensing the current variation due to the significant differences in the electrical resistivity between the amorphous and crystalline phases. The experimental results clearly show that a crystalline bit with approximately 30nm diameter can be produced and readback, in good agreement with the corresponding simulations of the write/read processes

Write strategies for multi-Terabit per square inch scanned-probe phase-change memories

notes: Development of new recording strategy and coding schemes that increase the storage density of scanning-probe memories by at least 50% and potentially up to 100% or more as compared to conventional approaches. Carried out in collaboration with, and co-authored by, the world-renowned IBM Zurich Research Laboratories (recipients of 4 Nobel Prizes). Formed part of EU €9.5M Project 'ProTeM' led (co-ordinated) by Wright. Selected for re-publication in Virtual Journal of Nanoscale Science and Technology (vol. 22, issue 19, 1/11/2011, www.vjnano.org) and featured story on www.physicscom.org (11/11/2011) Led to follow-on EU funding in form of CareRAMM NMP project on carbon memories (€2.6 million funding, Wright as co-ordinator).Copyright © 2010 American Institute of PhysicsA mark-length write strategy for multi-Terabit per square inch scanned-probe memories is described that promises to increase the achievable user density by at least 50%, and potentially up to 100% or more, over conventional approaches. The viability of the write strategy has been demonstrated by experimental scanning probe write/read measurements on phase-change (GeSbTe) media. The advantages offered by adopting mark-length recording are likely to be equally applicable to other forms of scanned probe storage

High-Precision Tuning of State for Memristive Devices by Adaptable Variation-Tolerant Algorithm

Using memristive properties common for the titanium dioxide thin film devices, we designed a simple write algorithm to tune device conductance at a specific bias point to 1% relative accuracy (which is roughly equivalent to 7-bit precision) within its dynamic range even in the presence of large variations in switching behavior. The high precision state is nonvolatile and the results are likely to be sustained for nanoscale memristive devices because of the inherent filamentary nature of the resistive switching. The proposed functionality of memristive devices is especially attractive for analog computing with low precision data. As one representative example we demonstrate hybrid circuitry consisting of CMOS summing amplifier and two memristive devices to perform analog multiply and accumulate computation, which is a typical bottleneck operation in information processing.Comment: 20 pages, 6 figure