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Royston, United Kingdom

Kroezen H.J.,Zernike Institute for Advanced Materials | Eising G.,Zernike Institute for Advanced Materials | Ten Brink G.,Zernike Institute for Advanced Materials | Palasantzas G.,Zernike Institute for Advanced Materials | And 2 more authors.
Applied Physics Letters | Year: 2012

The electrical properties of amorphous-crystalline interfaces in phase change materials, which are important for rewritable optical data storage and for random access memory devices, have been investigated by surface scanning potential microscopy. Analysis of GeSb systems indicates that the surface potential of the crystalline phase is ∼30-60 mV higher than that of the amorphous phase. This potential asymmetry is explained qualitatively by the presence of a Schottky barrier at the amorphous-crystalline interface and supported also by quantitative Schottky model calculations. © 2012 American Institute of Physics. Source

Wang L.,Nanchang Hangkong University | Wright C.D.,University of Exeter | Shah P.,Middlesex University | Aziz M.M.,University of Exeter | And 3 more authors.
Japanese Journal of Applied Physics | Year: 2011

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. © 2011 The Japan Society of Applied Physics. Source

Sebastian A.,IBM | Sebastian A.,University of Barcelona | Pauza A.,Plarion Ltd | Rossel C.,IBM | And 5 more authors.
New Journal of Physics | Year: 2011

The electrical transport and resistance switching mechanism in amorphous carbon (a-C) is investigated at the nanoscale. The electrical conduction in a-C thin films is shown to be captured well by a Poole-Frenkel transport model that involves nonisolated traps. Moreover, at high electric fields a field-induced threshold switching phenomenon is observed. The following resistance change is attributed to Joule heating and subsequent localized thermal annealing. We demonstrate that the mechanism is mostly due to clustering of the existing sp2 sites within the sp3 matrix. The electrical conduction behaviour, field-induced switching and Joule-heating-induced rearrangement of atomic order resulting in a resistance change are all reminiscent of conventional phasechange memory materials. This suggests the potential of a-C as a similar nonvolatile memory candidate material. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source

Ramachandraiah H.,KTH Royal Institute of Technology | Amasia M.,KTH Royal Institute of Technology | Cole J.,Plarion Ltd | Sheard P.,Plarion Ltd | And 4 more authors.
Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012 | Year: 2012

HIV is a pandemic that currently threatens over 33 million lives worldwide and HIV/AIDS remains one of the major causes of death globally. The continued monitoring of the CD4+ T-lymphocytes count in HIV patients is necessary for proper treatment, although this testing is too expensive and complex for limited resource settings. We report on a novel integrated centrifugal (CD) microfluidic system for rapid and low-cost HIV diagnosis through automated counting of CD4+ T-cells for point-of-care applications. We demonstrate the integrated T-cell immunocapture and detection mechanism using a novel system comprised of a modified commercial DVD drive and polymer disc. Source

Ramachandraiah H.,KTH Royal Institute of Technology | Amasia M.,KTH Royal Institute of Technology | Cole J.,Plarion Ltd | Sheard P.,Plarion Ltd | And 6 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2013

We present a novel "Lab-on-DVD" system and demonstrate its capability for rapid and low-cost HIV diagnostics by counting CD4+ cells isolated from whole blood. We show that a commercial DVD drive can, with certain modifications, be turned into an improved DVD-based laser scanning microscope (DVD-LSM). The system consists of a multi-layered disposable polymer disc and a modified commercial DVD reader with rotational control for sample handling, temperature control for optimized bioassay, a photodiode array for detection, and software for signal processing and user interface-all the necessary components required for a truly integrated lab-on-a-chip system, with the capability to deliver high-resolution images down to 1 μm in size. Using discs modified with antibodies, we specifically captured CD4+ cells from whole blood, demonstrating single cell resolution imaging. The novel integrated DVD platform with sub-micron image resolution brings, for the first time, affordable cellular diagnostic testing to the point-of-care and should be readily applicable at resource-limited settings. © 2013 The Royal Society of Chemistry. Source

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