Enhanced Light Emission from Si Nanocrystals Coupled to Plasmonics Structures

Abstract

Silicon (Si) is the material of choice for microelectronics but, as it happens to be an indirect band gap semiconductor, is also a poor light emitter. A great interest is arising on technologies able to integrate microelectronics and photonic devices on a single chip, in order for example to solve the technological problem known as the “interconnect bottleneck” on current microprocessors. In the last few years Si nano-crystals (NCs) have emerged as a promising technologies to increase the light emission of silicon. The study of the coupling between NCs and nano-antennas in order to further enhance the photoluminescence (PL) emission of the NCs is presented. Theoretically, it is important to shape the plasmonic nano-antennas, which sustain localized surface plasmons (LSPs) that increase the light matter interaction by several orders of magnitude, in order to produce the highest light emission from the NCs or the emitters. The experimental work consisted of the fabrication of the nano-antennas, such as nanostructures made via electron beam lithography (EBL) or colloidal nano-particles and their coupling to NCs, either directly under the surface of the substrate or placed from colloidal solution near them. PL and lifetime measurements via an optical microscope enabled us to measure the enhancement of the emission using a variety of parameters, depending both on the geometry of the nano-antennas and on the NCs′ fabrication process. Results obtained for the coupling of Si NCs and gold NPs formed by annealing a thin Au film showed an enhancement factor in the lifetime of three. The measurements done on nanocrystals embedded on a silica matrix which interacts with nanoantennas fabricated on top of the surface via EBL showed an increased PL emission of around 20.