  We show that the orientation of nitrogen-vacancy (NV) defects in diamond can
be efficiently controlled through chemical vapor deposition (CVD) growth on a
(111)-oriented diamond substrate. More precisely, we demonstrate that
spontaneously generated NV defects are oriented with a ~ 97 % probability along
the [111] axis, corresponding to the most appealing orientation among the four
possible crystallographic axes. Such a nearly perfect preferential orientation
is explained by analyzing the diamond growth mechanism on a (111)-oriented
substrate and could be extended to other types of defects. This work is a
significant step towards the design of optimized diamond samples for quantum
information and sensing applications.
