Fabrication of Two-Dimensional Arrays of CdSe Pillars Using E-Beam Lithography and Electrochemical Deposition

摘要

A two-dimensional (2D) periodic dielectric structure can mimic the periodic crystal potential of a semiconductro, and thus present a specific photonic bandgap associated with the details of the structure. Waveguides that are made of this so-called photonic crystal can guide light with great efficiency both along a straight path or around a sharp corner. There-fore, optically integrated circuits that are built on a chip have been made possible. Depending on the wavelength of the light source involved, the lattice constant of the commonly used photonic crystal falls within the submicrometer range. Moreover, the preparation of defect-free 2D photonic crystals with large index contrast is of fundamental importance here, because any undesirable defects can trap or emit photons. Various approaches have been developed to fabricate 2D and 3D crystals. for example, a common approach is the fabrication of 2D and 3D photonic crystals utilizing a colloidal assenmbly mechanism. Although this technique for making large-area photonic crystals is economic and relatively easy, the crystals suffer from inevitable unwanted defects. In view of this, interference lithography has emerged as a very powerful tool for the patterning of periodic structures. Neither colloidal assembly nor interference lithography as of yet can generate waveguide patterns by themselves. Pattern generation is generally accomplished by conventional photolithography techniques. In this study, we demonstrate a unique method for the fabrication of 2D arrays of CdSe pillars with large height-to-width ratio. Furthermore, we show that with this technique CdSe structures arranged in various patterns can be readily made. The fabrication technique utilizes electron beam exposure for crystal pattern definition, and electrochemical deposition for structure formation.