Reproducible fabrication and characterization of diamond membranes for photonic crystal cavities

Single crystal diamond has turned out to be a promising material for applications in quantum information processing for its ability to host color centers with optimal properties such as narrow emission lines or long-lived spin states. However, the mechanical properties of diamond like its hardness and chemical resistance make the fabrication of photonic devices challenging up to date. In this article, a method is presented to produce thin, free-standing single crystal diamond membranes. These membranes are characterized with four different techniques complementing one another and detecting defects or thickness variations in the diamond films with high accuracy. The precise characterization allows for reproducible fabrication of two-dimensional photonic crystal cavities by focused ion beam milling in the as-produced membranes. Furthermore, optimizations in focused ion beam milling are presented, reducing imperfections of the fabricated photonic crystal cavities. Together with post-processing and implantation of color centers, these diamond nanostructures are a building block for cavity coupling experiments toward reliable spin-photon interfaces or optomechanical devices. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim