Near-field photodetection with high spatial resolution by nanocrystal quantum dots

We report a new demonstration of nanoscale solution-processed photodetectors by fabricating a nano-sized gap between two electrodes and drop-casting nanocrystal quantum dots (NCQDs) into the gap. We demonstrate a detection sensitivity of 62 pW with a max responsivity of 2.7 mA/W over a device with a nano-gap of 25 nm. Additionally, we characterize the dependence of signal-to-dark current ratio and responsivity on nano-gap size. Responsivity ranges from 1 - 90 mA/W for a nano-gap size range of 25 nm - 1.5 nm. Our results represent the first demonstration of how near-field optical detection for sub-diffraction nanophotonic integrated circuits can be achieved in principle using NCQDs. (C) 2007 Optical Society of America.