Materials in Focus

- from  Materials Research Society,

Nitrogen n-dopes graphene

It is relatively easy to p-dope graphene using adsorbates and oxygen groups on edges, but for real-world applications, scientists need to be able to make n-doped material too. This is more difficult because special strategies are needed. A research team has now shown that graphene can be n-doped through high-power electrical joule heating in ammonia gas. They then made an n-type graphene FET that operates at room temperature.

Weak light beam flips magnetization in magnetic semiconductor
A research team has showed that a surprisingly feeble light beam can flip zeros to ones and vice versa, in a special magnetic layer. Although currently limited to very low temperatures, the apparently new effect might one day be extended to improve data storage. They grew a thin, crystalline layer of the gallium arsenide but replaced about one percent of the gallium atoms with the magnetic atom manganese.

Polymers indicate imminent failure by changing color
A new polymer changes color when stressed to the point of mechanical failure. The color change occurs by the addition of spiropyran molecules that undergo electrocyclic ring-opening in response to mechanical force. The resulting ring-opened merocyanine molecules are brightly colored, producing red or purple hues in the polymer, depending upon how the indicator molecule is covalently linked to the polymeric structure. The spiropyran essentially undergoes "a force-induced reaction inside of a solid structural polymer."

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