  Hexagonal Boron Nitride (hBN) mono and multilayers are promising hosts for
room temperature single photon emitters (SPEs). In this work we explore high
energy (~ MeV) electron irradiation as a means to generate stable SPEs in hBN.
We investigate four types of exfoliated hBN flakes - namely, high purity
multilayers, isotopically pure hBN, carbon rich hBN multilayers and monolayered
material - and find that electron irradiation increases emitter concentrations
dramatically in all samples. Furthermore, the engineered emitters are located
throughout hBN flakes (not only at flake edges or grain boundaries), and do not
require activation by high temperature annealing of the host material after
electron exposure. Our results provide important insights into controlled
formation of hBN SPEs and may aid in identification of their crystallographic
origin.
