General Strategy for Nanoscopic Light Source Fabrication

Abstract

IO N A general tendency in the development of nanotechnology is the miniaturization of electronic and photonic devices. Small-scale light emitters, such as nanolasers, are an important part of integrated nanophotonic devices. Thus, they have been given much research attention. [ 1 ] Currently, there are two independent techniques for the fabrication of nanolasers. One is based on lasing semiconductor nanowires where the nanowire acts as both the emitter and the cavity resonator. [ 2 ] Another is based on a lasing plasmon-assisted semiconductor nanowire, in which the light originates from the nanowire. In this confi guration, the optical modes are confi ned to the metal/semiconductor interface region, which acts as cavity resonator. [ 3 ] Based on the waveguide geometry at the nanometer scale, [ 4,5 ] the large discontinuity of the electric fi eld at the high-index-contrast interfaces can confi ne and enhance the intensity of the light fi eld in the low-index material when light is guided by total internal refl ection. Accordingly, we propose a facile and effective route for the fabrication of small-scale light emitters, which could serve as nanoscopic light sources. The luminescence emission from the nanocolumn is confi ned in the hollow region when a small hole is drilled in a luminescent semiconductor nanocolumn. Meanwhile, the size of the luminescent region of the nanocolumn is greatly reduced from the total nanocolumn to the small hole. Therefore, we can fabricate a smaller light source than would be possible using the nanocolumn alone via this unique strategy. In this paper, using the hollow ZnO nanocolumn as an example, we establish a theoretical model to address the basic physics involved in transport in a hollow luminescent semiconductor nanocolumn. Moreover, we demonstrate that by using such a nanostructure, the luminescence emission originating from the hollow ZnO nanocolumn can be confi ned to a low-index region (hollow region). This intensity is much higher than that which can be achieved at the edge of the ZnO nanocolumn. We then perform experiments to confi rm the validity of these theoretical results by measuring the cathodoluminescence (CL) spectra and images of an individual hollow hexagonal ZnO nanocolumn using scanning electron microscopy (SEM). Finally, computer simulations based on the fi nite element method corroborate our theoretical results and experimental fi ndings.