Electrical phase change of CVD-grown Ge-Sb-Te thin film device

A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film has been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The CVD-grown Ge-Sb-Te thin film shows promise for the phase change memory applications

Laser-induced forward transfer of thermoelectric materials on polymer and glass substrates

Laser-induced forward transfer (LIFT) is a laser-assisted direct write method that has been used to print a range of solids and rheological fluids. The donor that is to be printed is previously deposited onto a transparent support substrate that is usually referred to as a carrier. A highly energetic short-pulsed laser beam imaged through the transparent carrier onto the donor results in the forward transfer of a donor pixel onto a receiver substrate placed either in contact or a few microns apart. Solid films can be transferred with minimal change in their crystal and domain structure via LIFT

Differential diagnoses of fibrosing lung diseases

Objectives: To describe the challenges inherent in diagnosing fibrosing lung diseases (FLD) on CT imaging and methodologies by which the diagnostic process may be simplified. / Methods: Extensive searches in online scientific databases were performed to provide relevant and contemporary evidence that describe the current state of knowledge related to FLD diagnosis. This includes descriptions of the utility of a working diagnosis for an individual case discussed in a multidisciplinary team (MDT) setting and challenges associated with the lack of consensus guidelines for diagnosing chronic hypersensitivity pneumonitis. / Results: As well as describing imaging features that indicate the presence of a fibrosing lung disease, those CT characteristics that nuance a diagnosis of the various FLDs are considered. The review also explains the essential information that a radiologist needs to convey to an MDT when reading a CT scan. Lastly, we provide some insights as to the future directions the field make take in the upcoming years. / Conclusions: This review outlines the current state of FLD diagnosis and emphasizes areas where knowledge is limited, and more evidence is required. Fundamentally, however, it provides a guide for radiologists when tackling CT imaging in a patient with FLD. / Advances in knowledge: This review encompasses advice from recent guideline statements and evidence from the latest studies in FLD to provide an up-to-date manual for radiologists to aid the diagnosis of FLD on CT imaging in an MDT setting

Chalcogenide phase change materials for nanoscale switching

Since the demonstration of threshold switching in chalcogenide alloys over forty five years ago, phase change materials have been extensively investigated for switching and data storage applications. Phase change switching is based on the reversible change between crystalline and amorphous states of a material and in many chalcogenides this change of state takes place in nanoseconds

Ultra-fast calorimetry study of Ge₂Sb₂Te₅ crystallization between dielectric layers

Phase changes in chalcogenides such as Ge2Sb2Te5 can be exploited in non-volatile random-access memory, with fast crystallization crucial for device operation. Ultra-fast differential scanning calorimetry, heating at rates up to 40,000K s-1, has been used to study the crystallization of amorphous Ge2Sb2Te5 with and without sandwich layers of ZnS-SiO2. At heating rates up to 1000K s-1, the sandwich layers retard crystallization, an effect attributed to crystallization-induced stress. At greater heating rates (>or = 5000K s-1), and consequently higher crystallization temperatures, the stress is relaxed, and sandwich layers catalyze crystallization. Implications for memory-device performance are discussed

All-optical image recognition and processing with plasmonic metasurfaces

We engage effective nonlinearity of the coherent wave interaction on a thin metamaterial absorber to demonstrate all-optical image recognition and logical functions that in principle can be performed at THz frame rates and quantum-limited intensities

Crystallisation study of the Cu₂ZnSnS₄ chalcogenide material for solar applications

Second generation thin-film chalcogenide materials, in particular CuInGa(S,Se)2 (CIGS) and CdTe, have been among the most promising and quickly became commercial candidates for large-scale PV manufacturing. These materials offer stable and efficient (above 10%) photovoltaic modules fabricated by scalable thin-film technologies and cell efficiencies above 20 % (CIGS). Indium-free kesterite-related materials such as Cu2ZnSnS4 have attracted significant research interest due to their similar properties to CIGS. In these materials, indium is replaced with earth-abundant zinc and tin metals. The quaternary semiconductor Cu2ZnSnS4(CZTS) is a relatively new photovoltaic material and is expected to be interesting for environmentally amenable solar cells, as its constituents are nontoxic and abundant in the Earth's crust. The CZTS thin films show p-type conductivity, a band gap of 1.44–1.51 eV that is ideal to achieve the highest solar-cell conversion efficiency, and relatively high optical absorption in the visible light range

Optically reconfigurable metadevices based on phase-change materials

Chalcogenide phase-change media provide a uniquely flexible platform for both nanostructured and optically-rewritable all-dielectric metamaterials. Non-volatile, laser-induced phase transitions enable resonance switching in nanostructured chalcogenide meta-surfaces and allow for reversible direct-writing of arbitrary meta-devices in chalcogenide thin films, including dynamically refocusable, chromatically correctable and super-oscillatory lenses, and near-infrared-resonant photonic metamaterials

Phase-change chalcogenide glass metamaterial

Combining metamaterials with functional media brings a new dimension to their performance. Here we demonstrate substantial resonance frequency tuning in a photonic metamaterial hybridized with an electrically/optically switchable chalcogenide glass. The transition between amorphous and crystalline forms brings about a 10% shift in the near-infrared resonance wavelength of an asymmetric split-ring array, providing transmission modulation functionality with a contrast ratio of 4:1 in a device of sub-wavelength thickness.Comment: 3 pages, 3 figure

Fabrication and aero dynamic levitation of chalcogenide glass spheres

Spheres of gallium-lanthanum sulphide (GLS) and gallium lanthanum sulphite (GLSO) have been produced by laser irradiation on a copper hearth. Although similar fabrication techniques have been applied to oxide glasses, the technique has been overlooked for the production of chalcogenide glasses due to the perceived problem of the volatility of the chalcogens. In this work, glass microspheres of GLS/GLSO have been fabricated by laser irradiation of micron size irregular shaped glass particles on a Cu plate. In this material we found that evaporation of sulphur was not substantial as it appears to be more strongly chemically bound [1]. In addition to this method we have also established that it is possible to form larger spheres (mm diameter) of GLSO by aerodynamic levitation and laser heating using a CO2 laser (10.6 µm wavelength). Our studies involve overheating and supercooling of liquids and melts, outgassing analysis, high temperature resistivity measurements, and crystallization/structural studies [1-3]. In both fabrication methods the glasses could be melted and re-vitrified with low sulphur mass loss. We conclude that the production of glass spheres by laser irradiation[4] from irregular shaped starting material on a substrate using the wetting principle has substantial benefits for making microspheres and nanospheres