‘Tantalizing’ clues about why a mysterious material switches from conductor to insulator

Nanowerk  May 18, 2020 Researchers in Japan created crystals of tantalum disulfide and then cleaved the crystals in a vacuum to reveal ultra-clean surfaces which they examined, at a temperature close to absolute zero. Using quantum tunneling they studied the degree of conducting behavior of the material. The results showed that there was indeed a stacking of layers which effectively arranged them into pairs. Sometimes the crystals cleaved between the pairs of layers, and sometimes through a pair, breaking it. They performed spectroscopy on both the paired and unpaired layers and found that even the unpaired ones are insulating, leaving […]

Dirty carbon reveals a sophisticated side

MIT News  April 27, 2020 Polycyclic heavy hydrocarbons (HHs) such as coal, tar, and pitch are a family of materials with extremely rich and complex chemistry, representing a massive opportunity for their use in a range of potential applications. An international team of researchers (USA – MIT, industry, Canada, China) shows that optimal selection of initial HHs based on molecular constituents is essential in tuning the material for a particular and targeted electronic application. Combining the selection of feedstock chemistry (H:C and aromatic content) and controlling variable laser treatment parameters (laser power, speed, and focus) lead to full control over […]

Unlocking promising properties to create future technologies

EurekAlert  April 30, 2020 The manifestation of quantization in macroscopic physical systems has showcased important quantum phenomena, such as quantized conductance in (fractional) quantum Hall effects and quantized vortices in superconductors. An international team of researchers (USA – Rensselaer Polytechnic Institute, Florida State University, UT Dallas, Arizona State University, Japan, Hong Kong) reported the experimental observation of quantized exciton energies in a macroscopic system with strong Coulomb interaction, monolayer WSe2 crystal under a strong magnetic field. This work demonstrates the optical version of the QHE for excitons, and the researchers believe it will open the door for further discovery and […]

Researchers created a tiny circuit through a single water molecule

Phys.org  April 20, 2020 Water molecules can mediate charge transfer in biological and chemical reactions by forming electronic coupling pathways. Through molecular-level (Duke University, Arizona State University, Pennsylvania State University, UC Davis) has shown that there are two distinct states of water, corresponding to parallel and perpendicular orientations of the molecules. Water molecules switch from parallel to perpendicular orientations on applying an electric field, producing a switch from high- to low-conductance states, thus enabling the determination of single water molecular dipole moments. Water-water interactions affect the atomic-scale configuration and conductance of water molecules. These findings demonstrate the importance of the […]

Novel graphene-based filters to make gas purification more effective

Nanowerk  March 27, 2020 Precise molecular sieving is potentially possible using graphene oxide‐based membranes, if the porosity can be matched with the kinetic diameters of the gas molecules, which is possible via the tuning of graphene oxide interlayer spacing to take advantage of gas species interactions with graphene oxide channels. An international team of researchers (Australia, South Korea) have shown highly effective separation of gases from their mixtures by using uniquely tailored porosity in mildly reduced graphene oxide (rGO) based membranes. The study will lead to new avenues for the applications of graphene for efficiently separating CO2 from N2 and […]

Researchers identify breaking point of conducting material

EurekAlert  March 4, 2020 Accurate predictions of the temperature when embrittlement occurs is crucial to design conducting polymers that are used in next-generation flexible electronics. An international team of researchers (USA – Pennsylvania State University, Germany) found a way to measure glass transition temperatures by keeping track of the mechanical properties as embrittlement occurs, laying the foundation for understanding the relationship between the glass transition and structure. Follow-up studies then determined the glass transition for 32 different polymers by measuring mechanical properties as a function of temperature. They showed the simple relationship between the chemical structure and the glass transition […]

New encapsulation technique protects electronic properties of sensitive materials

Science Daily January 29, 2020 Indium selenide and gallium selenide are emerging two-dimensional semiconductors with appealing electronic properties. However, they are sensitive to air and device fabrication processes which induce structural damage and hamper their intrinsic properties. An international team of researchers (USA -Columbia University, Germany, Japan) has demonstrated an encapsulating technique where two layers of hBNhexagonal boron nitride (hBN) entirely covers the 2D layers of InSe and GaSe passivating them from the environment and isolating them from the charge disorder at the SiO2 surface. They demonstrated a strong and reproducible photo response and long-term stability. The technique can open […]

Scientists develop ceramic materials that are IR-transparent

Nanowerk  December 30, 2019 An international team of researchers (Ukraine, Russia, China) developed Y2O3-MgO nanocomposite ceramics with uniform distribution of two phases, microhardness over 11 GPa, and average grain size of 250 nm. It is capable of transmitting over 70% of IR-range with wavelength up to 6,000 nm. The IR transparency increases with the increasing of sintering temperatures, and top values are reached at 1,300-1,350 °C. This is due to the increase of sample density, grain growth, and the reduction of grain boundary length. Due to the submicron size of the grains and their even distribution in the whole volume […]

An alloy that retains its memory at high temperatures

Science Daily  December 3, 2019 In the conventional high-temperature shape memory alloy Ti-Ta, the formation of this phase compromises completely the shape memory effect. Addition of other elements to form Ti-Ta-X alloys often modifies the transformation temperatures. Researchers in Germany used transparent descriptors derived from first-principles calculations to search for new ternary Ti-Ta-X alloys that combine stability and high temperatures. They suggest four alloys with these properties, namely Ti-Ta-Sb, Ti-Ta-Bi, Ti-Ta-In, and Ti-Ta-Sc. Their predictions for the most promising of these alloys, Ti-Ta-Sc, are subsequently fully validated by experimental investigations showing no traces of omega phase after cycling. Their computational […]

Controlling the optical properties of solids with acoustic waves

Science Daily  December 2, 2019 So far moderately large changes in the exitons control parameters — temperature, pressure, electric and magnetic fields that can tune excitonic properties have only been achieved under equilibrium conditions and at low temperatures. An international team of researchers (Switzerland, Spain, Germany, USA- Simons Foundation Flatiron Institute, France) has demonstrated the control of excitonic properties using acoustic waves in titanium dioxide at room temperature. To do this, the researchers launched a high-frequency (hundreds of gigahertz), large-amplitude acoustic wave in the material using ultrashort laser pulses. This strategy allows for the dynamical manipulation of the exciton properties […]