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Two-Dimensional Materials Could Make the Ink for Printable Electronics

Researchers overcome manufacturing bottleneck for producing molybdenum disulfide for a printable solution

2 min read
Two-Dimensional Materials Could Make the Ink for Printable Electronics

Researchers at the National University of Singapore (NUS) have developed an exfoliation method for the two-dimensional (2D) material molybdenum disulfide that leads to crystals of the substance becoming high quality monolayer flakes. These flakes can made into a solution that could be used for printable photonics and electronics.

NUS researchers have been on a bit of a run lately in developing novel manufacturing techniques for 2D materials. Last month, researchers there developed a one-step method for producing graphene for wafer scale films. This latest work also presents improved manufacturing methods for 2D materials, but this time the material of choice is molybdenum disulfide (MoS2), which is itself gaining some favor over graphene in electronics applications. However, the exfoliation technique developed by the NUS team can be applied to other 2D materials such as such as tungsten diselenide and titanium disulfide.

These materials represent a class of chalcogenide compounds. When chalcogens, like sulfur or selenium, are combined with transition metals, like molybdenum or tungsten, they form transition metal dichalcogenides. So far only a few of these transition metal dichalcogenides have been investigated for their electronic properties,   but early indications have shown them to be promising for optoelectronic devices such as thin film solar, photodetectors and flexible logic circuits.

However, the process for turning them into a single, printable layer takes a long time and the yield is quite poor. To address this issue, the NUS researchers explored the use of metal adducts (a compound made from two or more substances) of naphthalene. The researchers created naphthalenide adducts of lithium, sodium and potassium and compared the exfoliation efficiency and quality of molybdenum disulfide produced from each. The research appears today's edition of Nature Communications.

The researchers were able to produce high quality single-layer molybdenum disulfide sheets with large flake sizes, and also demonstrated that exfoliated molybdenum disulfide flakes can be made into a printable solution. With this solution, the researchers were able to show that the ink could produce wafer-size films.

“At present, there is a bottleneck in the development of solution-processed two dimensional chalcogenides,” said Professor Loh Kian Ping, who heads the Department of Chemistry at the NUS, in a press release. “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.”

In future research, the NUS team will be looking at creating inks from different 2D chalcogenides using its novel method.

Photo: National University of Singapore

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The First Million-Transistor Chip: the Engineers’ Story

Intel’s i860 RISC chip was a graphics powerhouse

21 min read
Twenty people crowd into a cubicle, the man in the center seated holding a silicon wafer full of chips

Intel's million-transistor chip development team

In San Francisco on Feb. 27, 1989, Intel Corp., Santa Clara, Calif., startled the world of high technology by presenting the first ever 1-million-transistor microprocessor, which was also the company’s first such chip to use a reduced instruction set.

The number of transistors alone marks a huge leap upward: Intel’s previous microprocessor, the 80386, has only 275,000 of them. But this long-deferred move into the booming market in reduced-instruction-set computing (RISC) was more of a shock, in part because it broke with Intel’s tradition of compatibility with earlier processors—and not least because after three well-guarded years in development the chip came as a complete surprise. Now designated the i860, it entered development in 1986 about the same time as the 80486, the yet-to-be-introduced successor to Intel’s highly regarded 80286 and 80386. The two chips have about the same area and use the same 1-micrometer CMOS technology then under development at the company’s systems production and manufacturing plant in Hillsboro, Ore. But with the i860, then code-named the N10, the company planned a revolution.

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