Microelectrode-Less Control of Semiconducting Fluorescent Nanoparticles By Dielectrophoretic (DEP) Force for High Degree of Freedom

Abstract

In previous our research, we introduced attachment or detachment of 25nm diameter quantum dots (QDs) manipulating method and 100nm diameter polystyrene (PS) nano-beads at nano sized metal structures by dielectrophoretic (DEP) force. The metal nano-structures were connected with micro electrode to apply the DEP force for trapping the nanoparticles. The DEP force is easily controllable by frequency and intensity of applied electric field. And the DEP force is very sufficient to manipulate the fluorescent nanoparticles at specific nanostructures, due to the large difference of electric fields inducement around nanostructures. The trapped fluorescent nanoparticles at nano metal structures which can be considered and called as a composited structure of photon emitting nanoparticles and nano structures could be utilized in study of coupling photons to plasmon waveguides as a real single photon generator. And the nanoparticle manipulating method could accomplish the additional composite structures without any chemical reactions as a lithographic method of fluorescent nanoparticles which can be used in QD display. The QDs are the most important and remarkable candidates nanoparticles to produce photon-emitting in quantum devices and display. However, the previous research had limitations such as limiting the variety of nanostructure, degree of freedom, and attaching sites due to the connected microelectrodes. And additional fabrication steps should be needed after the manipulation of nanoparticles to metal structures. In this paper, we introduced the manipulation of QD which is composed with cadmium selenide, the semiconducting materials at the nanostructures by DEP force for plasmonic applications and QD display. For the high degree of freedom, the nanostructures didn’t connect with microelectrodes. Various shapes of nano structures which is made of gold are accomplished between the micro electrodes. The microelectrodes were not connected with the nano-structures. Wire, Y-branch and vertex shape of nanostructure were fabricated with e-beam lithography and lift-off process. The distance between microelectrodes and nanostructures was also calculated to optimize the condition of QD trapping with multiphysics simulation. Possibility of selective manipulation of QDs was also performed through the theoretical approaches at various shape of nanostructures by using the DEP force. Each shape of structures was considered to manipulate the QDs at the nanostructures. The selective manipulation which is attaching-side, position, end-facet selective in nanostructures provide the three degrees of freedom in attachment in the same structure. Consequently, the semiconductor materials based fluorescent nanoparticles, QDs, are successfully manipulated at nano-structures without any connecting with microelectrodes.