Positioning of quantum dots on metallic nanostructures

Abstract

The capability to position individual emitters, such as quantum dots, near metallicnanostructures is highly desirable for constructing active optical devices that canmanipulate light at the single photon level. The emergence of the field of plasmonics as ameans to confine light now introduces a need for high precision and reliability inpositioning any source of emission, which has thus far been elusive. Placing an emissionsource within the influence of plasmonic structures now requires accuracy approachingmolecular length scales. In this paper we report the ability to reliably position nanoscalefunctional objects, specifically quantum dots, with sub-100-nm accuracy, which is severaltimes smaller than the diffraction limit of a quantum dot’s emission light. Electron beamlithography-defined masks on metallic surfaces and a series of surface chemicalfunctionalization processes allow the programmed assembly of DNA-linked colloidalquantum dots. The quantum dots are successfully functionalized to areas as small as(100 nm)2 using the specific binding of thiolated DNA to Au/Ag, and exploiting thestreptavidin–biotin interaction. An analysis of the reproducibility of the process for variouspattern sizes shows that this technique is potentially scalable to the single quantumdot level with 50 nm accuracy accompanied by a moderate reduction in yield.