  We report on the creation and characterization of Pb-related color centers in
diamond upon ion implantation and subse- quent thermal annealing. Their optical
emission in photoluminescence (PL) regime consists of an articulated spectrum
with intense emission peaks at 552.1 nm and 556.8 nm, accompanied by a set of
additional lines in the 535700 nm range. The attribution of the PL emission to
stable Pb-based defects is corroborated by the correlation of its intensity
with the implantation fluence of Pb ions, while none of the reported features
is observed in reference samples implanted with C ions. Furthermore, PL
measurements performed as a function of sample temperature (143-300 K range)
and un- der different excitation wavelengths (532 nm, 514 nm, 405 nm) suggest
that the complex spectral features observed in Pb-implanted diamond might be
related to a variety of different defects and/or charge states. This work
follows from previous reports on optically active centers in diamond based on
group IV impurities, such as Si, Ge and Pb. In perspective, a comprehensive
study of this set of defect complexes could bring significant insight on the
common features involved in their formation and opto-physical properties, thus
offering a solid basis for the devel- opment of a new generation of
quantum-optical devices.
