Saturday, 5 April 2014

Improvements to graphene detectors

Last June, I noted research in Singapore which promised a wide-ranging imaging sensor based on graphene. The hyperspectral detection of graphene ranges from ultraviolet to far infrared but there has been a problem with very low sensitivity of the single layer of carbon atoms.

A paper in Nature Nanotechnology, published on March 16 2014, outlines a method devised by researchers at the University of Michigan whereby electrons freed by photons hitting a first layer of graphene tunnel through an insulating barrier layer and into a second graphene layer. This affects current flowing through the second graphene layer and this is what is detected. The result is a dramatic increase in sensitivity as well as IR detectors that perform well at room temperatures. This is all explained in a press release from the University of Michigan. The 'trick' was to look into how the signal could be amplified, rather than making the signal itself stronger. (I haven't read the whole paper but I would ask what noise does this generate.)

"We can make the entire design super-thin," said Zhaohui Zhong, assistant professor of electrical and computer engineering at Michigan, and one of the inventors. "It can be stacked on a contact lens or integrated with a cell phone." This mention of contact lenses led the Register to ask "Want to see at night? Here comes the infrared CONTACT LENS".

A patent, 'Photodetector based on double layer heterostructures', has been applied for.