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f. Pre-exfoliated molybdenum disulphide g. Sodium-exfoliated single layer molybdenum disulphide dispersion in water


Using a two-step expansion and intercalation method, the researchers were able to produce high quality single-layer molybdenum disulphide sheets with unprecedentedly large flake size.


The researchers also demonstrated that the exfoliated molybdenum disulphide flakes can be made into a printable solution, and wafer-size films can be printed, as the good dispersion and high viscosity of the flakes render it highly suitable for inkjet printing.


In a comparative analysis, Zheng Jian, the first author of the paper, found that the alkali metal naphthalenide intercalation method applied possesses significant advantages in comparison to the conventional method.


exfoliated by their novel method so as to produce printable optoelectronic devices. They will also be testing the optical non-linear properties of the flakes they have produced.


ESA’s billion-star surveyor lifts off


The two telescopes used for surveillance incorporate mirrors fabricated from silicon carbide


On 19th December, ESA’s Gaia mission blasted off on a Soyuz rocket from Europe’s Spaceport in Kourou, French Guiana, on its exciting mission to study a billion suns.


Gaia is destined to create the most accurate map yet of the Milky Way. By making accurate measurements of the positions and motions of 1 percent of the total population of roughly 100 billion stars, it will answer questions about the origin and evolution of our home Galaxy.


The two telescopes used for observation incorporate 190 × 69 mm mirrors fabricated from sintered SiC. The mirror surface is coated with a layer of SiC using CVD.


Zheng Jian, demonstrating the printing of Molybdenum disulphide flakes from a solution of the exfoliated flakes


Commenting on the significance of the findings, Loh says, “At present, there is a bottleneck in the development of solution-processed two dimensional chalcogenides. Our team has developed an alternative exfoliating agent using the organic salts of naphthalene and this new method is more efficient than previous solution-based methods. It can also be applied to other classes of two-dimensional chalcogenides.”


“Considering the versatility of this method, it may be adopted as the new benchmark in exfoliation chemistry of two-dimensional chalcogenides,” he adds.


Further research into printable devices


The fast growing field of printed photonics, electronics and optoelectronics demands high material quality, precise material deposition, and application-specific optical, electrical, chemical, and mechanical properties.


To further their research and to cater to the industry, Loh and his team will be looking at developing inks based on different types of two-dimensional chalcogenides


162 www.compoundsemiconductor.net January / February 2014


After a few glitches, the sunshield, which keeps Gaia at its working temperature and carries solar cells to power the satellite, was deployed in a ten minute automatic sequence, completed around eighty eight minutes after launch.


Gaia is now en route towards an orbit around a gravitationally-stable virtual point in space called L2, some 1.5 million kilometres beyond Earth as seen from the sun.


On 20th December, engineers commanded Gaia to perform the first of two critical thruster firings to ensure it is on the right trajectory towards its L2 home orbit. About twenty days after launch, the second critical burn will take place, inserting it into its operational orbit around L2.


A four-month commissioning phase will start on the way to L2, during which all of the systems and instruments will be turned on, checked and calibrated. Then Gaia will be ready to begin its five-year science mission.


Gaia’s sunshield will block heat and light from the sun and Earth, providing the stable environment needed by its sophisticated instruments to make an extraordinarily sensitive and precise census of the Milky Way’s stars.


“Gaia promises to build on the legacy of ESA’s first star- mapping mission, Hipparcos, launched in 1989, to reveal the history of the galaxy in which we live,” says Jean-


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