Application Investigation of HOPG by New PAC ⁶²Zn Probe Nuclei

An isotope separator on-line (ISOL) dedicated to on-line perturbed angular correlation (PAC) and positron annihilation spectroscopy (PAS) was constructed at CIAE based on HI-13 Tandem Accelerator, and a 30 keV radioactive beam of ⁶²Zn was produced by it. Using the ⁶²Zn radioactive beam, the defects in B doped highly oriented pyrolytic graphite (HOPG) were investigated from two angles of view by both positron annihilation Doppler broadening and perturbed angular correlation techniques. The physical performances of HOPG depend greatly on impurity-doping. Doping would induce defects in HOPG. No perturbation was observed in undopped HOPG and this indicates that the probe nuclei are located in the space between two basic planes. A strong perturbation were detected in B doped HOPG and the measured quadrupole interaction frequency ω₀ is 157 Mrad/s. It indicates that the ⁶²Zn probe nuclei are captured by the dislocation loops induced by B doping. The parameter S of the positron annihilation Doppler broadening measurement is obviously larger in B dopped HOPG than in undoped HOPG, and this demonstrates that B doping induces defects in HOPG. The results obtained by the perturbed angular correlation and the positron annihilation are in good agreement, which shows the defects are induced by B doping in HOPG.