  We demonstrate the controlled preparation of heteroepitaxial diamond nano-
and microstructures on silicon wafer based iridium films as hosts for single
color centers. Our approach uses electron beam lithography followed by reactive
ion etching to pattern the carbon layer formed by bias enhanced nucleation on
the iridium surface. In the subsequent chemical vapor deposition process, the
patterned areas evolve into regular arrays of (001) oriented diamond
nano-islands with diameters of <500nm and a height of approx. 60 nm. In the
islands, we identify single SiV color centers with narrow zero phonon lines
down to 1 nm at room temperature.
