Phys.org July 26, 2021 A team of researchers in the US (Virginia Tech, UC Santa Barbara) created a de-icing method based on Cassie’s Law, which shows that air can be trapped under water drops if the drops are suspended atop a structure that is bumpy and water-repellent. They sought to make ice form in a layer with lower adhesion to the surface. They created an array of pillars, each one millimeter tall by half a millimeter wide. The tiny pedestals were machined into a pattern with a millimeter between the pillars. As the temperature dropped, frost preferentially grew on the […]
Category Archives: Materials science
Cooling high power electronics – boron arsenide spreads heat better than diamond
Nanowerk July 9, 2021 A team of researchers in the US (UCLA, UC Irvine) explored the interface energy transport in semiconductor materials with high thermal conductivity, including boron arsenide (BAs) and boron phosphide (BP). They showed that BAs and BP cooling substrates can be heterogeneously integrated with metals, a wide-bandgap semiconductor (gallium nitride, GaN) and high-electron-mobility transistor devices. GaN-on-BAs structures exhibit a high thermal boundary conductance of 250 MW m−2 K−1, and comparison of device-level hot-spot temperatures with length-dependent scaling (from 100 μm to 100 nm) shows that the power cooling performance of BAs exceeds that of reported diamond devices. Operating AlGaN/GaN high-electron-mobility transistors with […]
Scientists Have Created a New Bendy And Flexible Form of Ice
Science Alert July 9, 2021 An international team of researchers (USA – UC Berkeley, China) used tungsten needle in a ultracold chamber around -50 deg C into which water vapor was released and applied an electric field. Water molecules were attracted to the tip of the needle, where they crystallized, forming a microfiber with a maximum width of around 10 micrometers. When the temperature was lowered to between minus 70 and minus150 degrees Celsius they were able to bend. At minus 150 degrees Celsius, the microfiber 4.4 micrometers across was able to bend into a nearly circular shape, with a […]
Ultrathin semiconductors are electrically connected to superconductors for the first time
Phys.org July 6, 2021 For future applications in electronics and quantum technology, researchers are focusing on the development of new components that consist of monolayer semiconducting material. An international team of researchers (Switzerland, Japan) has demonstrated superconducting vertical interconnect access (VIA) contacts to a monolayer of molybdenum disulfide (MoS2) using MoRe as a contact material. The electron transport was mostly dominated by a single superconductor/normal conductor junction with a clear superconductor gap. They found MoS2 regions that are strongly coupled to the superconductor resulting in resonant Andreev tunneling and junction-dependent gap characteristics, suggesting a superconducting proximity effect. Magnetoresistance measurements showed […]
A crystal made of electrons
Phys.org July 1, 2021 An international team of researchers (Switzerland, USA – Harvard University, Germany, Japan) has succeeded in observing Wigner crystals which consist of only electrons predicted almost ninety years ago. The team used optical spectroscopy to demonstrate that electrons in a monolayer semiconductor with density lower than 3 × 1011 per centimetre squared. The combination of a high electron effective mass and reduced dielectric screening enabled them to observe electronic charge order even in the absence of a moiré potential or an external magnetic field. The findings demonstrate that charge-tunable transition metal dichalcogenide monolayers enable the investigation of […]
Making the invisible visible
Science Daily May 20, 2021 It has so far been difficult to gain a more accurate picture of the course of chemical reactions at the atomic level. An international team of researchers (Germany, USA – UC Berkeley, UC San Diego, SLAC National Accelerator Laboratory, France) has shown second harmonic generation on a table-top extreme ultraviolet source. To investigate the surface of titanium sample down to the atomic level they set up a special focusing geometry, consisting of an elliptically shaped mirror to concentrate the laser radiation onto a small area. They focused the radiation with a wavelength of 32.8 nanometres […]
A new ‘gold standard’ compound for generating electricity from heat
Phys.org May 26, 2021 The principal challenges in current thermoelectric power generation modules are the availability of stable, diffusion-resistant, lossless electrical and thermal metal–semiconductor contacts that do not degrade at the hot end nor cause reductions in device efficiency. Transverse thermoelectrics avoid this problem by producing a current that runs perpendicular to the conducting device, requiring contacts only on the cold end of the generator. However, the materials known to create this sideways voltage are impractically inefficient. A team of researchers in the US (Ohio State University, University of Illinois) demonstrated that a layered crystal consisting of the elements rhenium […]
Lighting it up: Fast material manipulation through a laser
Phys.org April 21, 2021 An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. Controlling the electrons’ arrangement has been a key topic for decades. An international team of researchers (Germany, Sweden, US – research organization) has massively cut down the switching time to only 100 femtoseconds by shooting ultrashort optical laser pulses at a semi-metallic crystal composed of tungsten and tellurium atoms. Shining light on the crystal encourages it to reorganize its internal electronic structure, which also changes the conductivity of the crystal. They […]
Discovery could help lengthen lifespan of electronic devices
Science Daily April 9, 2021 Ferroelectric materials are subjected to repeated mechanical and electrical loading, leading to a progressive decrease in their functionality, ultimately resulting in failure. An international team of researchers (Australia, China, USA – Pacific Northwest National Laboratory) observed ferroelectric fatigue as it occurred using in-situ biasing transmission electron microscopy. They discovered that charge accumulation at domain walls is the main reason of the formation of c domains, which are less responsive to the applied electric field. The rapid growth of the frozen c domains leads to the ferroelectric degradation. This finding gives insights into the nature of […]
Scientists discover three liquid phases in aerosol particles
Phys.org April 12, 2021 Aerosol particles fill the atmosphere and play a critical role in air quality. These particles contribute to poor air quality and absorb and reflect solar radiation, affecting the climate system. An international team of researchers (Canada, USA – UC Irvine, Pacific Northwest National Laboratory, Harvard University, Georgia Institute of Technology, Germany) used optical and fluorescence microscopy, to present images that showed the coexistence of two noncrystalline phases for real-world samples as well as for laboratory-generated samples under simulated atmospheric conditions. The results revealed that atmospheric particles can undergo liquid–liquid phase separations. The study focused on particles […]