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calmond writes:
"Researchers from the University of Michigan have created a super-thin light detector that can pick up the entire infrared spectrum in addition to visible and ultraviolet light. The heat vision technology is made of graphene, which is considered to be the world's strongest material, and is small enough to fit on a contact lens.
Its developers say the technology could one day give people super-human vision and is particularly relevant for use by the military. Other, non-military uses, such as checking power distribution cables or search-and-rescue tasks are also possible.
A news release from the University team is to be found here, while a technical abstract is here. Unfortunately, the full technical paper is only viewable by payment or membership.
(Score: 5, Informative) by bd on Thursday March 20 2014, @05:15PM
Well, they do explicitly give you the responsivity at 1300 nm, 2100 nm and 3200 nm in the paper. From that, you can easily calculate the responsivity from R=\eta\frac{e}{h\nu}
I get:
1300 nm: \eta=3.8
2100 nm: \eta=1.12
3200 nm: \eta=0.43
So this device doesn't really have internal amplification after 2100 nm. What I am puzzled by is the time response curve in figure 2. That looks like some _slow_ dynamics going on there.
(Score: 3, Informative) by hubie on Thursday March 20 2014, @06:53PM
I'm still having a hard time getting my head wrapped around this. It looks like the visible data in Figure 2 use a Ta2O5 tunneling barrier, but the IR data in Figure 4 use a silicon barrier. I'm trying to put this in the context of what would the response be for a single broadband device (as hinted at in the press release), and I don't think you can get there from the paper. Also, unless there is some dramatic rise in the QE, it is dropping pretty fast by the time you get to 3200 nm, and so I wouldn't expect it to be too great at 5000 nm for the MWIR, and it would be awfully small out in the LWIR.
I don't know anything about growing graphene layers so I also wonder what the limitations are on making pixelated detectors. Can you make an array of these with unit cells comparable to what you can with silicon and InGaAs?
(Score: 5, Interesting) by bd on Thursday March 20 2014, @09:24PM
Yeah, I am a bit disappointed with the quality of the paper. Especially that they did not go below 1300 nm in the device with the Si barrier. I guess below 1100 nm the photons are above the band gap of the barrier and something funny happens with the device. Maybe not, but if they don't demonstrate it, I'm not convinced. That would leave us with a slow photo-detector that is not that impressive at all...
The press release really reads like a bad peace of science fiction.