  Color centers in hexagonal boron nitride (hBN) are presently attracting broad
interest as a novel platform for nanoscale sensing and quantum information
processing. Unfortunately, their atomic structures remain largely elusive and
only a small percentage of the emitters studied thus far has the properties
required to serve as optically addressable spin qubits. Here, we use confocal
fluorescence microscopy at variable temperature to study a new class of point
defects produced via cerium ion implantation in thin hBN flakes. We find that,
to a significant fraction, emitters show bright room-temperature emission, and
good optical stability suggesting the formation of Ce-based point defects.
Using density functional theory (DFT) we calculate the emission properties of
candidate emitters, and single out the CeVB center - formed by an interlayer Ce
atom adjacent to a boron vacancy - as one possible microscopic model. Our
results suggest an intriguing route to defect engineering that simultaneously
exploits the singular properties of rare-earth ions and the versatility of
two-dimensional material hosts.
