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Graphene... excellent analog material... and sensor (via Nature)


Unless you have been meditating in an isolation tank for the last several years, you have probably heard about the wonder material known as graphene. The one-atom thick carbon allotrope has potential applications in everything from highly efficient, super-fast integrated circuits to super-capacitors capable of insane power storage. The list of graphene applications shows no sign of stopping anytime soon and researchers from the University of Michigan have added to the ever-growing list with their graphene-based light detector. The room-temperature light detector is the first in the world to ‘sense’ the full spectrum of infrared wavelengths and doesn’t need extensive cooling to do so. The material is actually great at capturing visible and ultraviolet light (great for graphene-based solar cells) but poor at grabbing infrared light because it can’t absorb enough of it to generate a detectable electrical signal. To get around that issue, the researchers, headed by assistant professor Zhaohui Zhong, derived a new way to detect those electrical signals, not by measuring them directly when the spectrum hits the graphene but rather by looking at how to amplify that signal.

 

The team looked at how a nearby current is affected by the electrical discharges of infrared light as it hits the graphene material. They then took that information and designed a device that’s able to detect infrared’s signal wavelengths by sandwiching and insulating material between two sheets of graphene. A current is run through the bottom layer and when light hits the top layer, it frees electrons creating positively charged holes. Then using a ‘quantum mechanical’ trick, the electrons then pass through the holes (bypassing the insulating layer) to the bottom graphene layer. The positively charged holes on the top layer produce an electric field that affects the current flow on the bottom layer, which the team used to measure the change in current, allowing them to calculate the brightness of the light hitting the material. The advancement could lead to contact lenses that allow the wearer to have infrared ‘heat’ vision or could be used in sensors that monitor hostile or volatile environments that are dangerous for humans. While the contact lenses don’t yet exist, you can bet the military will be working on functional prototypes sometime in the near future.

 

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