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New Electronic Material

First speedy transistors made from an ultrathin material.

Source: “Single-Layer MoS2 Transistors”
Andras Kis et al.
Nature Nanotechnology 6: 147-150

Electric mineral: When peeled to make sheets just three atoms thick, this mineral, called molybdenite, is a promising material for making circuits and solar cells.

Results: Researchers made high-performance transistors from ultrathin sheets of a mineral called molybdenite, which is used as a lubricant and is relatively inexpensive.

Why it matters: Materials that are just a few atoms thick have unusual electrical and optical properties that make them promising candidates to replace or complement silicon and other traditional materials. Single-layer molybdenite is two-dimensional, transparent, flexible, and highly conductive. The transistors are the first high-performance devices to be made from the material; this early work suggests it could be used in fast, low-power digital logic circuits as an alternative to silicon, which is reaching its limits. Molybdenite could also offer advantages for making higher-performance flexible solar cells and light-emitting diodes for displays.

Methods: Researchers manually crushed molybdenite and used tape to peel apart the crystals layer by layer until fragments just three atoms thick were left. They deposited these thin films on a substrate, added an insulating material, and used standard methods to add source and drain electrodes and a gate to make a transistor.

Next Steps: The researchers will try to make devices out of other ultrathin materials in the same class as molybdenite, such as tungsten disulfide.

Skinny Super-conductors

Thinner cables could lead to more efficient transmission and stronger magnetic fields

Source: “Compact GdBa2Cu3O7-δ coated conductor cables for electric power transmission and magnet applications”
D. C. van der Laan et al.
Superconductor Science & Technology 24: 042001

Results: Researchers have used rare earth metals to make superconducting cables that are one-tenth the diameter of existing versions and far more flexible.

Why it matters: Conventional superconducting cables can carry currents about 10 times as strong as those carried by copper wires. They can also reduce energy losses in power transmission and produce extremely strong magnetic fields. But a 7.5-­centimeter-thick cable structure is used to protect the superconducting material, seriously limiting its applications. The thinner cables—which are less than a centimeter wide—could be installed onboard military airplanes and ships to carry the high currents needed for lasers and other equipment. They could greatly increase the capacity of transmission cables in conduits under city streets, and they could be wound tightly to create magnetic fields far more intense than is possible today. That would be useful for applications such as particle accelerators and proton therapy, a type of radiation treatment.

Methods: Researchers discovered that a relatively new class of superconductors based on rare earth metals could withstand much higher mechanical strain than existing superconductors. They designed cables that made use of the materials’ high tolerance for compressive forces: they’re wrapped in tight bends around a copper form that’s much thinner than the ones in conventional cables.

Next Steps: The researchers are developing versions of the cables that are even more flexible. They are also testing the cables’ ability to generate strong magnetic fields.

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