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June 05, 2012

Quantum dot graphene photodetector is a billion times more sensitive and Graphene bolometer out performs commercial silicon bolometers by 100,000 times

1. ZDNet - Researchers working at the Institute of Photonic Sciences (ICFO) in Barcelona have built a super-sensitive photodetector by combining graphene with semiconducting quantum dots that outperforms other graphene based devices by a billion times.

This is a follow up on an article from the middle of May.

Speaking to PhysicsWorld , lead researcher Gerasimos Konstantatos explains: “We managed to successfully combine graphene with semiconducting nanocrystals to create complete new functionalities in terms of light sensing and light conversion to electricity."
Nature Nanotechnology - Hybrid graphene–quantum dot phototransistors with ultrahigh gain

Graphene is an attractive material for optoelectronics1 and photodetection applications because it offers a broad spectral bandwidth and fast response times. However, weak light absorption and the absence of a gain mechanism that can generate multiple charge carriers from one incident photon have limited the responsivity of graphene-based photodetectors to ~10−2 A W−1. Here, we demonstrate a gain of ~10^8 electrons per photon and a responsivity of ~10^7 A W−1 in a hybrid photodetector that consists of monolayer or bilayer graphene covered with a thin film of colloidal quantum dots. Strong and tunable light absorption in the quantum-dot layer creates electric charges that are transferred to the graphene, where they recirculate many times due to the high charge mobility of graphene and long trapped-charge lifetimes in the quantum-dot layer. The device, with a specific detectivity of 7 × 10^13 Jones, benefits from gate-tunable sensitivity and speed, spectral selectivity from the short-wavelength infrared to the visible, and compatibility with current circuit technologies.





8 pages of supplemental material


2. Nature Nanotechnology - Dual-gated bilayer graphene hot-electron bolometer

Graphene is an attractive material for use in optical detectors because it absorbs light from mid-infrared to ultraviolet wavelengths with nearly equal strength. Graphene is particularly well suited for bolometers—devices that detect temperature-induced changes in electrical conductivity caused by the absorption of light—because its small electron heat capacity and weak electron–phonon coupling lead to large light-induced changes in electron temperature. Here, we demonstrate a hot-electron bolometer made of bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The bolometer exhibits a noise-equivalent power (33 fW Hz–1/2 at 5 K) that is several times lower, and intrinsic speed (over 1 GHz at 10 K) three to five orders of magnitude higher than commercial silicon bolometers and superconducting transition-edge sensors at similar temperatures


5 pages of supplemental material


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