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nanotimes News in Brief

most promising terahertz technologies are based on small semiconductor transistor-like structures that are able to modulate a terahertz signal at room tem- perature, which is a significant advantage over ear- lier modulators that could only operate at extremely cold temperatures. Unfortunately, these transistor- like devices rely on a thin layer of metal called a “metal gate” to tune the terahertz signal. This metal gate significantly reduces the signal strength and limits how much the signal can be modulated to a lackluster 30%.

By replacing the metal gate with a single layer of graphene, the researchers have predicted that the modulation range can be significantly expanded to be in excess of 90%. This modulation is controlled by applying a voltage between the graphene and semiconductor. Unlike the metal gate modulator, the graphene design barely diminished the output power of the terahertz energy. Made up of a one- atom-thick sheet of carbon atoms, graphene boasts a host of amazing properties: it’s remarkably strong, a superb thermal insulator, a conductor of electrici- ty, and now a better means to modulate terahertz radiation.

Berardi Sensale-Rodriguez, Tian Fang, Rusen Yan, Mi- chelle M. Kelly, Debdeep Jena, Lei Liu, and Huili (Gra- ce) Xing: Unique prospects for graphene-based terahertz modulators, In: Applied Physics Letters, Vol. 99(2011), Article 113104 [3 pages], DOI:10.1063/1.3636435 http://dx.doi.org/10.1063/1.3636435

11-09 :: September 2011

Jin-Woo Han and Meyya Meyyappan at the Cen- ter for Nanotechnology at NASA Ames Research Center in Moffett Field, USA, have developed a new flexible memory fabric woven together from interlocking strands of copper and copper-oxide wires. At each juncture, or stitch along the fabric, a nanoscale dab of platinum is placed between the fibers. This “sandwich structure” at each crossing forms a resistive memory circuit. Resistive memory has received much attention due to the simplicity of its design.

© Meyya Meyyappan (ARC-T) / Jin-Woo Han (ARC-RD/USRA)

The copper-oxide fibers serve as the storage medi- um because they are able to change from an insula- tor to a conductor simply by applying a voltage.

The copper wires and the platinum layers serve as the bottom and top electrodes, respectively. This design easily lends itself to textiles because it natu- rally forms a crossbar memory structure where the fibers intersect.