  Fabrication of devices designed to fully harness the unique properties of
quantum mechanics through their coupling to quantum bits (qubits) is a
prominent goal in the field of quantum information processing (QIP). Among
various qubit candidates, nitrogen vacancy (NV) centers in diamond have
recently emerged as an outstanding platform for room temperature QIP. However,
formidable challenges still remain in processing diamond and in the fabrication
of thin diamond membranes, which are necessary for planar photonic device
engineering. Here we demonstrate epitaxial growth of single crystal diamond
membranes using a conventional microwave chemical vapor deposition (CVD)
technique. The grown membranes, only a few hundred nanometers thick, show
bright luminescence, excellent Raman signature and good NV center electronic
spin coherence times. Microdisk cavities fabricated from these membranes
exhibit quality factors of up to 3000, overlapping with NV center emission. Our
methodology offers a scalable approach for diamond device fabrication for
photonics, spintronics, optomechanics and sensing applications.
