  Single crystal, nanoscale diamond membranes are highly sought after for a
variety of applications including nanophotonics, nanoelectronics and quantum
information science. However, so far, the availability of conductive diamond
membranes remained an unreachable goal. In this work we present a complete
nanofabrication methodology for engineering high aspect ratio, electrically
active single crystal diamond membranes. The membranes have large lateral
directions, exceeding 500x500 um2 and are only several hundreds of nanometers
thick. We further realize vertical single crystal p-n junctions, made from the
diamond membranes that exhibit onset voltages of ~ 10V and a current of several
mA. Moreover, we deterministically introduce optically active color centers
into the membranes, and demonstrate for the first time a single crystal
nanoscale diamond LED. The robust and scalable approach to engineer the
electrically active single crystal diamond membranes, offers new pathways for
advanced nanophotonics, nanoelectronics and optomechanics devices employing
diamond.
