Synchrotron-laser interactions in hexagonal boron nitride: an examination of charge trapping dynamics at the boron K-edge

Synchrotron–laser pump-probe (PP) luminescence measurements have been undertaken in hexagonal-phase boron nitride. For non-resonant excitation below the boron K-edge, the dynamics of the transients induced by the application of laser probes at 1.49, 2.33 and 3.07 eV are determined, as well as the signal recovery to equilibrium after the probes are removed. The transients are shown to be entirely related to the presence of trapping states within the material. By varying the synchrotron pump energy, the system dynamics are shown to change significantly, due to alteration in competition between the defect centres. As the synchrotron energy is scanned across the near-edge x-ray absorption (NEXAFS) region of the boron K-edge (190–205 eV), PP NEXAFS can be extracted directly from the trapping rate changes, and this opens the possibilities for directly linking particular charge trapping centres with their chemical environments. This is the first report where such processes have been used to obtain luminescence-based PP x-ray absorption spectra.