Science Daily August 11, 2021 A team of researchers in the US (University of North Florida, University of Illinois, Arizona State University) has demonstrated a new electronic phenomenon they call “asymmetric ferroelectricity” in atomic layer superlattices constructed using three constituent phases, CaTiO3, SrTiO3 and BaTiO3. The stacking sequence of the atomic layers is found to control the symmetry of the high-temperature dielectric response. When a nanostructured asymmetric strain is programmed into the lattice via the stacking order, the natural symmetry at high temperatures is removed and a polarized sample is obtained in which the polarization increases as the temperature is […]
Tag Archives: Advanced materials
Quantum materials cloak thermal radiation
Nanowerk August 11, 2021 For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and noncontact thermometry. A team of researchers in the US (University of Wisconsin–Madison, Harvard University, Purdue University, Brookhaven National Laboratory) has demonstrated that ultrathin thermal emitters that violate this one-to-one relationship via the use of samarium nickel oxide (SmNiO3), a strongly correlated quantum material that undergoes a fully reversible, temperature-driven solid-state phase transition. Due to the smooth and hysteresis-free nature of this unique insulator-to-metal phase transition enabled them to engineer the temperature dependence of […]
Effective EMI shielding behavior of thin graphene/PMMA nanolaminates
Phys.org August 4, 2021 The use of graphene in a form of discontinuous flakes in polymer composites limits the full exploitation of the unique properties of graphene, thus requiring high filler loadings for achieving satisfactory electrical and mechanical properties. An international team of researchers (Greece, Italy) produced centimetre-scale CVD graphene/polymer nanolaminates by using an iterative ‘lift-off/float-on’ process. These have outperformed, for the same graphene content, state-of-the-art flake-based graphene polymer composites in terms of mechanical reinforcement and electrical properties. The thin laminate materials have shown a high electromagnetic interference (EMI) shielding effectiveness, reaching 60 dB for a small thickness of 33 μm, […]
Molecular library of OLED host materials
Nanowerk July 27, 2021 OLED pixels normally consist of multiple layers which ensure, for example, that electrons can travel in the pixel with as little resistance as possible. The fine-tuning of the layer properties, for example, electron mobility or the emitted wavelength (color of the light), is a complex task. An international team of researchers (South Korea, Ukraine, Belgium, Germany) compared a wide range of computer-simulated and experimentally measured properties of OLED thin films, trying to understand whether OLED design can be guided solely by computer. They established a molecular library of typical OLED materials to streamline the design of […]
Through the thin-film glass, researchers spot a new liquid phase
Phys.org July 27, 2021 The structure of a glass closely resembles the liquid phase, but its properties are like solids, akin to a crystal. In vapor deposition, a material is changed from a gas into a solid directly. Researchers at the University of Pennsylvania used vapor deposition to create very dense thin-film glasses, corresponding to the packing of the new liquid phase, with a density much higher than was predicted to be possible without applying immense amounts of pressure. Thin films of these glasses can have density values even higher than crystal. Detailed structural information analysis of how individual molecules […]
Achilles heel of graphene exposed
Nanowerk July 19, 2021 The quantum Hall effect is the seminal example of topological protection as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. In conventional Hall bar geometries, topological protection of graphene edge channels is found less robust than in high mobility semi-conductors. An international team of researchers (Belgium, Germany, Japan) exploring graphene quantum Hall regime at the local scale revealed that the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels triggering topological breakdown. The finding is a major step forward in the understanding of the quantum Hall effect […]
Future information technologies: Topological materials for ultrafast spintronics
Phys.org July 16, 2021 To understand how fast excited electrons in the bulk and on the surface of Sb react to the external energy input, and to explore the mechanisms governing their response an international team of researchers (Germany, Russia, Ireland) used time-, spin- and angle-resolved photoemission to femtosecond-laser excitation. The data showed a ‘kink’ structure in transiently occupied energy-momentum dispersion of surface states, which can be interpreted as an increase in effective electron mass. They were able to show that this mass enhancement plays a decisive role in determining the complex interplay in the dynamical behaviors of electrons from […]
Harnessing the dark side
Nanowerk July 13, 2021 Optical singularities, which appear completely dark, typically occur when the phase of light with a specific wavelength, or color, is undefined. Researchers at Harvard University have developed a new way to control and shape optical singularities. The metasurface tilts the wavefront of light in a very precise manner over a surface so that the interference pattern of the transmitted light produces extended regions of darkness. Their approach allows precise engineering of dark regions with remarkably high contrast. Engineered singularities could be used to trap atoms in dark regions and improve super high-resolution imaging. As darkness has […]
New ‘Metafabric’ Passively Cools The Human Body by Almost 5 Degrees Celsius
Science Alert July 13, 2021 The metafabric developed by researchers in China uses titanium oxide-polylactic acid composite nanoparticles laminated with a thin layer of polytetrafluoroethylene (PTFE). It is designed to strongly reflect visible light (VIS), mid-infrared (MIR) and ultraviolet (UV) ranges. The wide distribution of nanoparticles, when combined with PTFE nanobeads, provides broad-spectrum scattering and reflectivity across the UV-VIS-NIR band. They tested the material in clear sky conditions measuring the temperature of the fabric in comparison to other common materials lying on a panel. Under peak solar irradiance between 11:00 and 15:00, the temperature of the metafabric was approximately 5.0°, […]
Mosquito-resistant clothing prevents bites in trials
Phys.org July 13, 2021 An international team of researchers (USA – North Carolina State University, Germany) has developed a mathematical model for fabric barriers that resist bites from Aedes aegypti mosquitoes based on textile physical structure and no insecticides. The model was derived from mosquito morphometrics and analysis of mosquito biting behavior. Woven filter fabrics, precision polypropylene plates, and knitted fabrics were used for model validation. Based on the model predictions, prototype knitted textiles and garments were developed that prevented mosquito biting, and comfort testing showed the garments to possess superior thermophysiological properties. The fabrics provided a three-times greater bite […]